As of December 31, 2019, subsequent to the adoption of ASC 321, the investment in Li Auto was accounted for as an equity investment at fair value, using the measurement alternative, given Li Auto was still a privately-held company at that time. The investment was recorded in long-term investment. In July 2020, Li Auto completed its initial public offering on the Nasdaq Global Select Market (“Li Auto IPO”) and the shares held by the Company were converted to Class A ordinary shares of Li Auto. Upon the completion of Li Auto IPO, the Company reclassified this investment from equity investments without readily determinable fair value to equity investments with readily determinable fair value. This security is valued using the market approach based on the quoted prices in active markets at the reporting date. The Company classifies the valuation techniques that use these inputs as Level 1 of fair value measurements.


	As of December 31,
	2020		2021
	RMB		RMB		US$

Debt securities:
Held-to-maturity time deposit		584,229,003		1,803,362,875		282,986,987
Equity securities:
Marketable wealth management products		71,584,410		330,857,592		51,918,777
Marketable investment in Li Auto		3,686,543,199		464,715,237		72,923,961

Total short-term investments		4,342,356,612		2,598,935,704		407,829,725

The gross unrecognized holding gain or loss on the held-to-maturity time deposit was RMB nil and RMB nil (US$ nil) as of December 31, 2020 and 2021, respectively. For the years ended December 31, 2019, 2020 and 2021, interest income related to debt securities was RMB51,574,467, RMB34,901,335 and RMB26,373,471 (US$4,138,573), respectively.

Changes in fair value due to the fluctuation of the share price are recognized in net gain (loss) on equity securities while changes in fair value due to the fluctuation of the foreign exchange rate are recognized in other comprehensive income (loss).