U.S. GAAP establishes a three-tier fair value hierarchy to classify and disclose all assets and liabilities measured at fair value on a recurring basis, as well as assets and liabilities measured at fair value on a non-recurring basis, in periods subsequent to their initial measurement. The hierarchy requires us to use observable inputs when available and to minimize the use of unobservable inputs when determining fair value. The three tiers are defined as follows:

•Level 1 - Observable inputs based on unadjusted quoted prices in active markets for identical assets or liabilities;

•Level 2 - Inputs, other than quoted prices in active markets, that are observable either directly or indirectly; and

•Level 3 - Unobservable inputs for which there is little or no market data and which require us to develop our own estimates and assumptions reflecting those that a market participant would use.

The asset or liability’s fair value measurement level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Valuation techniques maximize the use of relevant observable inputs and minimize the use of unobservable inputs. There were no instruments measured at fair value on a recurring basis using significant unobservable inputs as of March 31, 2024 and December 31, 2023.

•Market approach - Uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities;

•Income approach - Uses valuation techniques to convert future amounts to a single present amount based on current market expectations about those future amounts; and

•Cost approach - Based on the amount that currently would be required to replace the service capacity of an asset (i.e., replacement cost).

The carrying amounts of our restricted cash, accounts receivable, accounts payable, and accrued expenses approximate fair value as of March 31, 2024 and December 31, 2023 because of the relatively short duration of these instruments. Additionally, the carrying value of our debt associated with the term loan facility approximates fair value because the interest rates are variable and reset on relatively short durations to the then market rates.

Our investment portfolio has historically consisted largely of debt investments classified as available-for-sale. Changes in the fair value of available-for-sale securities, excluding other-than-temporary impairments, have been recorded in ‘Accumulated other comprehensive income (loss)’ in our consolidated balance sheets.

As of March 31, 2024, our cash and cash equivalents totaled $170.1 million, of which $86.0 million was held in readily available checking accounts or overnight repurchase investment accounts, and $84.1 million was held in money market funds with less than 90 days of maturity. Our cash and cash equivalents are classified as Level 1 assets. We did not hold any short- or long-term investments as of March 31, 2024.


	As of December 31, 2023
	Fair Value Measurement							Balance Sheet Classification
	Fair Value Level	Cost Basis		Unrealized Gains (Losses)		Fair Value		Cash and Cash Equivalents		Short-term Investments and Marketable Securities
Cash	Level 1	$	—	$	—	$	93,029	$	93,029	$	—
Money market fund	Level 1	56,322		—		56,322		56,322		—
U.S. Treasury bonds	Level 1	4,830		(2)		4,828		—		4,828


Agency bonds	Level 2	4,828		(3)		4,825		—		4,825
Total investments		$	65,980	$	(5)	$	159,004	$	149,351	$	9,653

We did not hold any Level 3 assets at any point during the three months ended March 31, 2024 and 2023. Additionally, there were no transfers between Levels 1 and 2 during the three months ended March 31, 2024 and 2023. Interest income on our investments totaled $1.9 million and $2.1 million for the three months ended March 31, 2024 and 2023, respectively.

The contractual maturities of our debt securities as of December 31, 2023 were all one year or less. Actual maturities may differ from contractual maturities because borrowers have the right to call or prepay certain obligations.