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The Company and Summary of Significant Accounting Policies | 12 Months Ended
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Dec. 31, 2021
The Company and Summary of Significant Accounting Policies |
The Company and Summary of Significant Accounting Policies | Note 1. The Company and Summary of Significant Accounting Policies The Company AXT, Inc. (“AXT”, “the Company”, “we,” “us,” and “our” refer to AXT, Inc. and its consolidated subsidiaries) is a worldwide materials science company that develops and produces high-performance compound and single element semiconductor substrates, also known as wafers. Our consolidated subsidiaries produce and sell certain raw materials some of which are used in our substrate manufacturing process and some of which are sold to other companies. ​ Our substrate wafers are used when a typical silicon substrate wafer cannot meet the conductive requirements of a semiconductor or optoelectronic device. The dominant substrates used in producing semiconductor chips and other electronic circuits are made from silicon. However, certain chips may become too hot or perform their function too slowly if silicon is used as the base material. In addition, optoelectronic applications, such as LED lighting and chip-based lasers, do not use silicon substrates because they require a wave form frequency that cannot be achieved using silicon. Alternative or specialty materials are used to replace silicon as the preferred base in these situations. Our wafers provide such alternative or specialty materials. We do not design or manufacture the chips. We add value by researching, developing and producing the specialty material wafers. We have two product lines: specialty material substrates and raw materials integral to these substrates. In 2021, our substrate product group generated 75% of our revenue and raw materials product group generated 25%. Our compound substrates combine indium with phosphorous (indium phosphide: InP) or gallium with arsenic (gallium arsenide: GaAs). Our single element substrates are made from germanium (Ge). Our raw materials include purified gallium, InP based material and pBN crucibles. We use purified gallium in producing our GaAs substrates and also sell purified gallium in the open market to other companies for use in magnetic materials, high temperature thermometers and growing single crystal ingots including gallium arsenide, gallium nitride, gallium antimonite, gallium phosphide and other materials and alloys. Pyrolytic boron nitride (pBN) crucibles are used in the high temperature (typically in the range 500 C to 1,500 C) growth process of single crystal ingots and epitaxial layer growth in MBE reactors. We use these pBN crucibles in our own ingot growth processes and also sell them in the open market to other companies. Principles of Consolidation The consolidated financial statements include the accounts of AXT, and our consolidated subsidiaries, Beijing Tongmei Xtal Technology Co., Ltd. (“Tongmei”), AXT-Tongmei, Inc. (“AXT-Tongmei”), Baoding Tongmei Xtal Technology Co., Ltd. (“Baoding Tongmei”), ChaoYang Tongmei Xtal Technology Co., Ltd. (“ChaoYang Tongmei”), ChaoYang LiMei Semiconductor Technology Co., Ltd. (“ChaoYang LiMei”), Nanjing JinMei Gallium Co., Ltd. (“JinMei”), ChaoYang JinMei Gallium Ltd. (“ChaoYang JinMei”), ChaoYang XinMei High Purity Semiconductor Materials Co., Ltd. (“ChaoYang XinMei”), MaAnShan JinMei Gallium Ltd., and Beijing BoYu Semiconductor Vessel Craftwork Technology Co., Ltd. (“BoYu”). Baoding Tongmei is located in the city of Dingxing, China. Each of ChaoYang Tongmei and ChaoYang LiMei is located in the city of Kazuo, China. All significant inter-company accounts and transactions have been eliminated. Investments in business entities in which we do not have controlling interests, but have the ability to exercise significant influence over operating and financial policies (generally 20-50% ownership), are accounted for by the equity method. For the years ended 2021 and 2020, we have five companies accounted for by the equity method. For the majority-owned subsidiaries that we consolidate, we reflect the portion we do not own as either noncontrolling interests in stockholder’s equity or as redeemable noncontrolling interests in temporary equity on our consolidated balance sheets and in our consolidated statements of operations. ​ When market conditions are warranted, we intend to construct facilities at the ChaoYang LiMei location to provide us with additional production capacity. For the years ended 2021 and 2020, expenses associated with ChaoYang LiMei had a de minimis impact on our consolidated financial statements. ​ As discussed in Note 6, “Investments in Privately-Held Raw Material Companies”, effective as of March 11, 2019, we reduced our ownership in Beijing JiYa Semiconductor Material Co., Ltd. (“JiYa”) from 46% to 39% by selling a portion of our JiYa shares to our investor partner, which is also JiYa’s landlord. As a result of this transaction, our investor partner became the largest shareholder of JiYa and assumed the right to appoint the general manager of JiYa and thereby exercised greater control over JiYa’s long-term strategic direction. Further, although our Chief Executive Officer remains on the board, as of March 11, 2019 he was no longer the chairman of JiYa’s board of directors and our Chief Financial Officer was no longer a member of JiYa’s board of financial supervisors. Therefore, we deconsolidated JiYa from our consolidated financial statements as of March 11, 2019 in accordance with Accounting Standards Codification (“ASC”) Topic 810, Consolidation (“ASC 810”). As of March 12, 2019, we accounted for our retained investment in JiYa under the equity method of accounting, as we continue to exercise significant influence. ​ Our consolidated balance sheet as of December 31, 2021 and 2020, as reported, does not include the assets and liabilities of JiYa, since we deconsolidated JiYa as of March 11, 2019. Our consolidated statement of operations for the year 2019 includes JiYa’s results for the period through March 11, 2019. ​ As discussed in Note 6, in May 2019, we purchased the remaining 3% ownership interest of JinMei from retiring members of the JinMei management team for approximately $413,000. As a result, our ownership of JinMei increased from 97% to 100%. As of June 1, 2019, we referred to JinMei as a wholly-owned subsidiary instead of a significantly controlled subsidiary and reduced the carrying value of the corresponding noncontrolling interests to zero. Before August 1, 2020, our ownership of ChaoYang JinMei was 100%. In August 2020, we sold an 8.5% ownership interest to current members of the ChaoYang JinMei management team for approximately $396,000. As a result, our ownership of ChaoYang JinMei decreased from 100% to 91.5%. As of August 2020, we referred to ChaoYang JinMei as a significantly controlled subsidiary instead of a wholly-owned subsidiary. ​ During the quarter ended December 31, 2020, Tongmei entered into two sets of definitive transaction documents, each consisting of a capital increase agreement along with certain supplemental agreements in substantially the same form (collectively, the “Capital Increase Agreements”), with several private equity investors in China. ​ In preparation for Tongmei’s application for a listing of shares in an initial public offering (the “IPO”) on the Shanghai Stock Exchange’s Sci-Tech innovAtion boaRd (the “STAR Market”), in late December 2020, we reorganized our entity structures in China. JinMei and BoYu and its subsidiaries were assigned to Tongmei and effectively merged with Tongmei although they retained their own respective legal entity status and are wholly owned subsidiaries of Tongmei. The 33% minority interest stakeholders of BoYu converted their ownership to a 7.59% minority interest in Tongmei. The 8.5% minority interest stakeholders, employees of JinMei, converted their ownership to a 0.38% minority interest in Tongmei. Further, a number of employees, key managers and contributors purchased a 0.4% minority interest in Tongmei. Additionally, Baoding Tongmei and ChaoYang Tongmei, were assigned to Tongmei as wholly owned subsidiaries. In 2020, the private equity funds (the “Investors”) had transferred approximately $48.1 million of new capital to Tongmei. An additional investment of approximately $1.5 million of new capital was funded in January 2021. Under China regulations these investments must be formally approved by the appropriate government agency and are not deemed to be dilutive until such approval is granted. The government approved the approximately $49 million investment in its entirety on January 25, 2021, at which time the Investors owned a redeemable noncontrolling interests in Tongmei of 7.28%. As of December 31, 2021, Tongmei’s noncontrolling interests and redeemable noncontrolling interests totaled approximately 14.5%. AXT remains the controlling stakeholder of Tongmei and holds a majority of the Board of Director positions of Tongmei. In June 2021, AXT sold AXT-Tongmei to Tongmei for $1. Since Tongmei is 85.5% owned by AXT, and the transaction was between common interest holders, the transaction was accounted for at net book value and resulted in an increase of $1.2 million to noncontrolling interests and $1.2 million to redeemable noncontrolling interests. ​ Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) requires management to make estimates, judgments and assumptions. We believe that the estimates, judgments, and assumptions upon which management relies are reasonable based on information available at the time that these estimates, judgments, and assumptions are made. These estimates, judgments, and assumptions can affect the reported amounts of assets and liabilities as of the date of the consolidated financial statements as well as the reported amounts of revenues and expenses during the periods presented. To the extent there are material differences between these estimates and actual results, our consolidated financial statements would be affected. Fair Value of Financial Instruments The carrying amounts of certain of our financial instruments including cash and cash equivalents, short-term investments and long-term investments, accounts receivable, accounts payable and accrued liabilities approximate fair value due to their short maturities. Certain cash equivalents and investments are required to be adjusted to fair value on a recurring basis. See Note 2. Fair Value of Investments ASC Topic 820, Fair value measurement (“ASC 820”) establishes three levels of inputs that may be used to measure fair value. Level 1 instruments represent quoted prices in active markets. Therefore, determining fair value for Level 1 instruments does not require significant management judgment, and the estimation is not difficult. Level 2 instruments include observable inputs other than Level 1 prices, such as quoted prices for similar instruments in markets with insufficient volume or infrequent transactions (less active markets), issuer bank statements, credit ratings, non-binding market consensus prices that can be corroborated with observable market data, model-derived valuations in which all significant inputs are observable or can be derived principally from or corroborated with observable market data for substantially the full term of the assets or liabilities, or quoted prices for similar assets or liabilities. These Level 2 instruments require more management judgment and subjectivity compared to Level 1 instruments, including:
| ● | Determining which instruments are most comparable to the instrument being priced requires management to identify a sample of similar securities based on the coupon rates, maturity, issuer, credit rating, and instrument type, and subjectively select an individual security or multiple securities that are deemed most similar to the security being priced.
| ● | Determining which model-derived valuations to use in determining fair value requires management judgment. When observable market prices for similar securities or comparable securities are not available, we price our marketable debt instruments using non-binding market consensus prices that are corroborated with observable market data or pricing models, such as discounted cash flow models, with all significant inputs derived from or corroborated with observable market data.
Level 3 instruments include unobservable inputs to the valuation methodology that are significant to the measurement of fair value of assets or liabilities. The determination of fair value for Level 3 instruments requires the most management judgment and subjectivity. We place short-term foreign currency hedges that are intended to offset the potential cash exposure related to fluctuations in the exchange rate between the United States dollar and Japanese yen. We measure the fair value of these foreign currency hedges at each month end and quarter end using current exchange rates and in accordance with generally accepted accounting principles. At quarter end any foreign currency hedges not settled are netted in “Accrued liabilities” on the consolidated balance sheets and classified as Level 3 assets and liabilities. As of December 31, 2021 and 2020, the net change in fair value from the placement of the hedge to settlement had a de minimis impact to the consolidated results. Foreign Currency Translation The functional currency of our Chinese subsidiaries is the renminbi, the local currency of China. Transaction gains and losses resulting from transactions denominated in currencies other than the U.S. dollar or in the functional currencies of our subsidiaries are included in “Other income, net” for the years presented. The transaction loss for the years ended December 31, 2021 and 2020 totaled $434,000 and $411,000, respectively. The transaction gain totaled $321,000 for the year ended December 31, 2019. The assets and liabilities of the subsidiaries are translated at the rates of exchange on the balance sheet date. Revenue and expense items are translated at the average rate of exchange for the period. Gains and losses from foreign currency translation are included in “Other comprehensive income (loss)”, net of tax in the consolidated statements of comprehensive income (loss). Revenue Recognition We manufacture and sell high-performance compound semiconductor substrates including indium phosphide, gallium arsenide and germanium wafers, and our consolidated subsidiaries sell certain raw materials, including high purity gallium (6N and 7N Ga), pyrolytic boron nitride (pBN) crucibles and boron oxide (B2O3). After we ship our products, there are no remaining obligations or customer acceptance requirements that would preclude revenue recognition. Our products are typically sold pursuant to purchase orders placed by our customers, and our terms and conditions of sale do not require customer acceptance. We account for a contract with a customer when there is a legally enforceable contract, which could be the customer’s purchase order, the rights of the parties are identified, the contract has commercial terms, and collectibility of the contract consideration is probable. The majority of our contracts have a single performance obligation to transfer products and are short term in nature, usually less than six months. Our revenue is measured based on the consideration specified in the contract with each customer in exchange for transferring products that are generally based upon a negotiated, formula, list or fixed price. Revenue is recognized when control of the promised goods is transferred to our customer, which is either upon shipment from our dock, receipt at the customer’s dock, or removal from consignment inventory at the customer’s location, in an amount that reflects the consideration we expect to be entitled to receive in exchange for those goods. ​ We have elected to account for shipping and handling as activities to fulfill the promise to transfer the goods. Shipping and handling fees billed to customers in a sales transaction are recorded as an offset to shipping and handling expenses. Sales taxes and value added taxes in foreign jurisdictions that are collected from customers and remitted to governmental authorities are accounted for on a net basis and, therefore, are excluded from revenue. ​ We do not provide training, installation or commissioning services. We provide for future returns based on historical data, prior experience, current economic trends and changes in customer demand at the time revenue is recognized. We do not recognize any asset associated with the incremental cost of obtaining revenue generating customer contracts. As such, sales commissions are expensed as incurred, given that the expected period of benefit is less than one year. Contract Balances We receive payments from customers based on a billing schedule as established in our contracts. Contract assets are recorded when we have a conditional right to consideration for our completed performance under the contracts. Accounts receivables are recorded when the right to this consideration becomes unconditional. We do not have any material contract assets as of December 31, 2021. ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | December 31, | ​ | December 31, | ​
​ | ​ | 2021 | ​ | 2020 | ​
Contract liabilities | ​ | $ | 946 | ​ | $ | 374 | ​
During the three and twelve months ended December 31, 2021, the Company recognized $3,000 and $266,000, respectively, of revenue that was included in the contract balances as of December 31, 2020. | ​ | ​ | ​ | ​ | ​ | ​
​ Disaggregated Revenue In general, revenue disaggregated by product types and geography (See Note 14) is aligned according to the nature and economic characteristics of our business and provides meaningful disaggregation of our results of operations. Since we operate in one segment, all financial segment and product line information can be found in the consolidated financial statements. Practical Expedients and Exemptions We elected to use the following practical expedients: (i) not to adjust the promised amount of consideration for the effects of a significant financing component when we expect, at contract inception, that the period between our transfer of a promised product or service to a customer and when the customer pays for that product or service will be one year or less; (ii) to expense costs as incurred for costs to obtain a contract when the amortization period would have been one year or less; (iii) not to assess whether promised goods or services are performance obligations if they are immaterial in the context of the contract with the customer. In addition, we do not disclose the value of unsatisfied performance obligations for contracts with an original expected length of one year or less. ​ Accounting for Sales Taxes We record sales taxes collected on sales of our products and for amounts not yet remitted to tax authorities as accrued liabilities on our consolidated balance sheets. Risks and Concentration of Credit Risk Our business is very dependent on the semiconductor, lasers and optical industries which can be highly cyclical and experience downturns as a result of economic changes, overcapacity, and technological advancements. Significant technological changes in the industry or customer requirements, or the emergence of competitive products with new capabilities or technologies, could adversely affect our operating results. In addition, a significant portion of our revenues and net income is derived from international sales. Fluctuations of the United States dollar against foreign currencies and changes in local regulatory or economic conditions, particularly in an emerging market such as China, could adversely affect operating results. We depend on a limited number of suppliers for certain raw materials, components and equipment used in manufacturing our products, including quartz tubing and polishing solutions. We generally purchase these materials through standard purchase orders and not pursuant to long-term supply contracts. Financial instruments that potentially subject us to concentration of credit risk consist primarily of cash and cash equivalents, investments, and accounts receivable. We invest primarily in money market accounts, certificates of deposit and corporate bonds. The composition and maturities are regularly monitored by management. Such deposits are in excess of the amount of the insurance provided by the federal government on such deposits. We are exposed to credit risks in the event of default by the issuers to the extent of the amount recorded on the consolidated balance sheets. ​ We perform ongoing credit evaluations of our customers’ financial condition, and limit the amount of credit extended when deemed necessary, but generally do not require collateral. The credit risk in our accounts receivable is mitigated by our credit evaluation process and the geographical dispersion of sales transactions. No customer accounted for more than 10% of our accounts receivable as of December 31, 2021 and two customers accounted for 11% and 10% of our accounts receivable as of December 31, 2020. No customers represented more than 10% of our revenue for the year ended December 31, 2021. One customer represented 11% of our revenue for the year ended December 31, 2020. One customer represented 15% of our revenue for the year ended December 31, 2019. Our top five customers, although not the same five customers for each period, represented 26% of our revenue for the year 2021, 32% of our revenue for 2020 and 40% of our revenue for 2019. For the years ended December 31, 2021 and 2020, one third-party customer for the raw materials products from our consolidated subsidiaries accounted for over 10% of the revenue from raw materials sales. For the year ended December 31, 2019, each of three third-party customers for the raw materials products from our consolidated subsidiaries accounted for over 10% of the revenue from raw materials sales. Our subsidiaries and raw material joint ventures are a key strategic benefit for us as they further diversify our sources of revenue. Cash and Cash Equivalents We consider investments in highly liquid instruments purchased with an original maturity of three months or less to be cash equivalents. Cash equivalents consist primarily of certificate of deposits. Cash and cash equivalents are stated at cost, which approximates fair value. Short-Term and Long-Term Investments We classify our investments in marketable securities as available-for-sale debt securities. Short-term and long-term investments are comprised of available-for-sale marketable securities, which consist primarily of certificates of deposit and corporate bonds. These investments are reported at fair value as of the respective balance sheet dates with unrealized gains and losses included in accumulated other comprehensive income (loss) within stockholders’ equity on the consolidated balance sheets. The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization is included in “Other income, net” in the consolidated statements of operations. Realized gains and losses and declines in value judged to be other than temporary on available-for-sale securities are also included in “Other income, net” in the consolidated statements of operations. The cost of securities sold is based upon the specific identification method. Accounts Receivable and Allowance for Doubtful Accounts and Sales Returns Accounts receivable are recorded at the invoiced amount and are not interest bearing. We periodically review the likelihood of collection on our accounts receivable balances and provide an allowance for doubtful accounts receivable primarily based upon the age of these accounts. We evaluate receivables from U.S. customers with an emphasis on balances in excess of 90 days and for receivables from customers located outside the U.S. with an emphasis on balances in excess of 120 days and establish a reserve allowance on the receivable balances if needed. The reason for the difference in the evaluation of receivables between foreign and U.S. customers is that U.S. customers have historically made payments in a shorter period of time than foreign customers. Foreign business practices generally require us to allow customer payment terms that are longer than those accepted in the United States. We assess the probability of collection based on a number of factors, including the length of time a receivable balance has been outstanding, our past history with the customer and their credit worthiness. We exercise judgment when determining the adequacy of these reserves as we evaluate historical bad debt trends, general economic conditions in the United States and internationally, and changes in customer financial conditions. Uncollectible receivables are recorded as bad debt expense when all efforts to collect have been exhausted and recoveries are recognized when they are received. As of December 31, 2021 and 2020, our accounts receivable, net balance was $34.8 million and $24.6 million, respectively, which was net of an allowance for doubtful accounts of $130,000 and $217,000 as of December 31, 2021 and 2020, respectively. During 2021, we decreased the allowance for doubtful accounts by $87,000 due to the write-off of accounts receivable for a customer. During 2020, the allowance for doubtful accounts increased by $183,000 due to the poor financial condition of a few customers. If actual uncollectible accounts differ substantially from our estimates, revisions to the estimated allowance for doubtful accounts would be required, which could have a material impact on our financial results for the future periods. As of December 31, 2021 and 2020, the sales returns reserve (included in accrued liabilities) balance was $48,000 and $81,000, respectively. During 2021, we utilized $48,000 and reserved an additional $15,000 and during 2020, we utilized $82,000 and reserved an additional $137,000. ​ Warranty Reserve We maintain a warranty reserve based upon our claims experience during the prior twelve months and any pending claims and returns of which we are aware. Warranty costs are accrued at the time revenue is recognized. As of December 31, 2021 and 2020, accrued product warranties totaled $743,000 and $609,000, respectively. The increase in accrued product warranties is primarily attributable to increased claims for quality issues experienced by approximately two of our customers. If actual warranty costs or pending new claims differ substantially from our estimates, revisions to the estimated warranty liability would be required, which could have a material impact on our financial condition and results of operations for future periods. Inventories Inventories are stated at the lower of cost (approximated by standard cost) or net realizable value. Cost is determined using the weighted average cost method. Our inventory consists of raw materials as well as finished goods and work-in-process that include material, labor and manufacturing overhead costs. We routinely evaluate the levels of our inventory in light of current market conditions in order to identify excess and obsolete inventory, and we provide a reserve for certain inventories to their estimated net realizable value based upon the age and quality of the product and the projections for sale of the completed products. When a reserve is recorded, a new lower cost basis for that inventory is established and subsequent changes in facts and circumstances do not result in the restoration or increase in the new cost basis. Property, Plant and Equipment Property, plant and equipment are stated at cost less accumulated depreciation computed using the straight-line method over the estimated economic lives of the assets, which vary from 1 to 39.5 years. Leasehold improvements are amortized using the straight-line method over the shorter of the estimated useful life or the term of the lease. We generally depreciate com puter, soft ware, office equipment, furniture and fixtures over 3 to 5 years, machinery and equipment over 1 to 20 years, automobiles over 5 to 10 years, leasehold and building improvements over 10 years, or the lease term if shorter, and buildings over 39.5 years. Repairs and maintenance costs are expensed as incurred. Impairment of Long-Lived Assets We evaluate property, plant and equipment and intangible assets for impairment. When events and circumstances indicate that long-lived assets may be impaired, we compare the carrying value of the long-lived assets to the projection of future undiscounted cash flows attributable to these assets. In the event that the carrying value exceeds the future undiscounted cash flows, we record an impairment charge against income equal to the excess of the carrying value over the assets’ fair value. Fair values are determined based on quoted market values, discounted cash flows or internal and external appraisals, as applicable. We did not recognize any impairment charges of long-lived assets in 2021, 2020 and 2019. Impairment of Investments All available-for-sale debt securities are periodically reviewed for impairment. An investment is considered to be impaired when its fair value is less than its amortized cost basis and it is more likely than not that we will be required to sell the impaired security before recovery of its amortized cost basis. Factors considered in determining whether a loss is temporary include the magnitude of the decline in market value, the length of time the market value has been below cost (or adjusted cost), credit quality, and our ability and intent to hold the securities for a period of time sufficient to allow for any anticipated recovery in market value. We also invest in equity instruments of privately-held companies in China for business and strategic purposes. Investments in our unconsolidated joint venture companies are classified as other assets and accounted for under either the equity or cost method, depending on whether we have the ability to exercise significant influence over their operations or financial decisions. We monitor our investments for impairment and record reductions in carrying value when events or changes in circumstances indicate that the carrying value may not be recoverable. Determination of impairment is highly subjective and is based on a number of factors, including an assessment of the strength of each company’s management, the length of time and extent to which the fair value has been less than our cost basis, the financial condition and near-term prospects of the subsidiary, fundamental changes to the business prospects of the company, share prices of subsequent offerings, and our intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in our carrying value. We estimate fair value of our cost method investments considering available information such as pricing in recent rounds of financing, current cash positions, earnings (loss) and cash flow forecasts, recent operational performance and any other readily available market data. We have 25% ownership interest in a germanium materials company in China, Tongli, and we incurred an impairment charge during 2019. After receiving such company’s preliminary first quarter 2019 financial results in early April 2019 and its projections for significant losses going forward, we determined that this asset was fully impaired and wrote the asset balance down to zero. This resulted in a $1.1 million impairment charge in our first quarter 2019 financial results. Except as mentioned above, there were no impairment charges for the remainder of these investments during the years ended December 31, 2021 and 2020. Segment Reporting We operate in one segment for the design, development, manufacture and distribution of high-performance compound and single element semiconductor substrates and sale of raw materials integral to these substrates. Our chief operating decision-maker has been identified as our Chief Executive Officer, who reviews operating results to make decisions about allocating resources and assessing our performance for the Company. We discuss revenue and capacity for both AXT and our joint ventures collectively, when determining capacity constraints and need for raw materials in our business, and consider their capacity when determining our strategic and product marketing and advertising strategies. While we consolidate our majority-owned or significantly controlled joint ventures, we do not allocate any portion of overhead, interest and other income, interest expense or taxes to them. We therefore have determined that our joint venture operations do not constitute an operating segment. Since we operate in one segment, all financial segment and product line information can be found in the consolidated financial statements. Stock-Based Compensation We have employee stock option plans, which are described more fully in Note 10—"Employee Benefit Plans and Stock-based Compensation”. We account for stock-based compensation in accordance with the provisions of ASC Topic 718, Compensation-Stock Compensation (“ASC 718”). We utilize the Black-Scholes option pricing model to estimate the grant date fair value of stock options, which requires the input of highly subjective assumptions, including estimating stock price volatility and expected term. Stock-based compensation cost is measured at each grant date, based on the fair value of the award, and is recognized as expense and as an increase in additional paid-in capital over the requisite service period of the award. Research and Development Research and development costs consist primarily of salaries, including stock-based compensation expense and related personnel costs, depreciation, materials and product testing which are expensed as incurred. Tangible assets acquired for research and development purposes are capitalized if they have alternative future use. ​ Advertising Costs Advertising costs, included in selling, general and administrative expenses, are expensed as incurred. Advertising costs for the years ended December 31, 2021, 2020 and 2019 were insignificant. Income Taxes We account for income taxes in accordance with ASC Topic 740, Income Taxes (“ASC 740”), which requires that deferred tax assets and liabilities be recognized using enacted tax rates for the effect of temporary differences between the book and tax bases of recorded assets and liabilities. ASC 740 also requires that deferred tax assets be reduced by a valuation allowance if it is more likely than not that a portion of the deferred tax asset will not be realized. The impact of ASC 740 is more fully described in Note 12. Comprehensive Income The components of other comprehensive income include unrealized gains and losses on marketable securities and foreign currency translation adjustments. Comprehensive income is presented in the consolidated statements of comprehensive income (loss). The balance of accumulated other comprehensive income is as follows (in thousands):
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | As of December 31,
​ |  | 2021 | ​ | 2020
Accumulated other comprehensive income: | ​ | ​ | ​ | ​ | ​ | ​
Unrealized gain (loss) on investments, net | ​ | $ | (65) | ​ | $ | 3
Cumulative translation adjustment | ​ |  | 7,041 | ​ | ​ | 3,601
​ | ​ |  | 6,976 | ​ | ​ | 3,604
Less: Cumulative translation adjustment attributable to noncontrolling interests and redeemable noncontrolling interests | ​ | ​ | 674 | ​ | ​ | 395
Accumulated other comprehensive income attributable to AXT, Inc. | ​ | $ | 6,302 | ​ | $ | 3,209
​ Net Income (Loss) Per Share Basic net income (loss) per share is computed using the weighted-average number of common shares outstanding during the periods less shares of common stock subject to repurchase and non-vested stock awards. Diluted net income (loss) per share is computed using the weighted-average number of common shares outstanding and potentially dilutive common shares outstanding during the periods. The dilutive effect of outstanding stock options and restricted stock awards is reflected in diluted earnings per share by application of the treasury stock method. Potentially dilutive common shares consist of common shares issuable upon the exercise of stock options and vesting of restricted stock awards. Potentially dilutive common shares are excluded from the computation of weighted-average number of common shares outstanding in net loss years, as their effect would be anti-dilutive to the computation. Recent Accounting Pronouncements In November 2021, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2021-10, Government Assistance (Topic 832): Disclosures by Business Entities about Government Assistance. ASU 2021-10 aims to provide increased transparency by requiring business entities to disclose information about certain types of government assistance they receive in the notes to the financial statements. The FASB broadly defined “government assistance” in Accounting Standards Codification (“ASC”) 832 to ensure that assistance received from most types of governmental entities or other related organizations would be disclosed. Government assistance within the scope of ASC 832 includes assistance that is administered by domestic, foreign, local (such as city, town, county, or municipality), regional (such as state, provincial, or territorial), national (federal) governments, as well as entities related to those governments (such as departments, independent agencies, boards, commissions, or component units). ASC 832 also includes government assistance from intergovernmental organizations (for example, global organizations such as the United Nations, regional organizations such as the European Union, and economic organizations such as the World Trade Organization). The guidance is effective for fiscal years beginning after December 15, 2021, with early application permitted. We are currently evaluating the impact the adoption of this ASU will have on our consolidated financial statements.

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