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Refund Liabilities (Tables) | 12 Months Ended
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Dec. 31, 2020
Accounting Policies [Abstract] |
Summary of Change in Refund Liabilities |
|  | December 31 |
|  | 2019 |  |  | 2020 |
|  | US$ |  |  | US$ |
Refund liabilities |  |  | 2,260 |  |  |  | 2,105 |
Estimated sales returns and other allowances are made and adjusted based on historical experience and the consideration of varying contractual terms. The changes in the refund liabilities are summarized as follows:
|  | Year Ended December 31 |
|  | 2019 |  |  | 2020 |
|  | US$ |  |  | US$ |
Refund liabilities |  |  |  |  |  |  |  |
Balance, beginning of year |  |  | 2,093 |  |  |  | 2,260 |
Additions |  |  | 5,076 |  |  |  | 10,576 |
Actual sales return and discount |  |  | (4,909 | ) |  |  | (10,731 | )
Balance, end of year |  |  | 2,260 |  |  |  | 2,105 |

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