5. Marketable securities

The following table summarizes marketable securities held at March 31, 2020 and December 31, 2019:


			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
March 31, 2020
Commercial paper	$	5,983	$	—	$	—	$	5,983
Corporate bonds		11,997		—		(4)		11,993
	$	17,980	$	—	$	(4)	$	17,976


			Gross		Gross
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
December 31, 2019
Commercial paper	$	11,940	$	—	$	—	$	11,940
Corporate bonds		11,990		20		—		12,010
U.S. Treasuries		13,484		5		—		13,489
	$	37,414	$	25	$	—	$	37,439

As of March 31, 2020, the Company held three securities that were in an unrealized loss position. The aggregate fair value of securities held by the Company in an unrealized loss position at March 31, 2020 was $8,993. These securities were in a gain position as of December 31, 2019. The Company determined that there was no material change in the credit risk of these securities. The Company does not intend to sell these securities and it is not more likely than not that the Company will be required to sell these securities before recovery of their amortized cost bases, which may be at maturity.

The Company has reviewed securities in an unrealized loss position at the individual security level and evaluated current expected credit loss by considering factors such as the nature of the investments, historical experience, market data, issuer-specific factors, and current economic conditions. During the three months ended March 31, 2020, the Company recognized no year-to-date credit loss related to short term marketable securities, and had no allowance for credit loss recorded as of March 31, 2020.