Note 3. Cash, Cash Equivalents and Short-Term Investments

Cash, cash equivalents and short-term investments consisted of the following as of December 31, 2019 and 2018:


	Carrying Value
	2019		2018
Cash	$	3,546,893	$	37,223,698
Cash equivalents:
Money market mutual fund		43,687,877		103,427
Total cash and cash equivalents		47,234,770		37,327,125
Short-term investments:
U.S. Treasury notes and bills		21,094,100		7,925,975
Mutual funds		25,966,686		2,004,993
Total short-term investments		47,060,786		9,930,968
Cash, cash equivalents and short-term investments	$	94,295,556	$	47,258,093

Available-for-sale investments

The amortized cost, gross unrealized gains, gross unrealized losses and fair value of available-for-sale investments by type of security at December 31, 2019 were as follows:


	Amortized		Unrealized		Unrealized
	Cost		Gains		Losses		Fair Value
U.S. Treasury notes		21,121,659		26,552		(54,111)		21,094,100
Total available-for-sale investments	$	21,121,659	$	26,552	$	(54,111)	$	21,094,100

There were no individual securities that have been in a continuous loss position of 12 months or greater as of December 31, 2019.

The following table summarizes the fair value of available-for-sale investments based on stated contractual maturities as of December 31, 2019:


	Amortized Cost		Fair Value
Due within one year	$	12,043,525	$	12,046,700
Due between one and two years		9,078,134		9,047,400
Total	$	21,121,659	$	21,094,100

The amortized cost, gross unrealized gains, gross unrealized losses and fair value of available-for-sale investments by type of security at December 31, 2018 were as follows:


	Amortized		Unrealized		Unrealized
	Cost		Gains		Losses		Fair Value
U.S. Treasury bills	$	2,948,777	$	19,523	$	—	$	2,968,300
U.S. Treasury notes		4,953,616		4,059		—		4,957,675
Total available-for-sale investments	$	7,902,393	$	23,582	$	—	$	7,925,975

The following table summarizes the fair value of available-for-sale investments based on stated contractual maturities as of December 31, 2018:


	Amortized Cost		Fair Value
Due within one year	$	5,913,327	$	5,936,515
Due between one and two years		1,989,066		1,989,460
Total	$	7,902,393	$	7,925,975

As of December 31, 2018, there were no available-for-sale investments in an unrealized loss position.

The primary objective of our investment portfolio is to enhance overall returns in an efficient manner while maintaining safety of principal, prudent levels of liquidity and acceptable levels of risk. Our investment policy limits interest-bearing security investments to certain types of debt and money market instruments issued by institutions with primarily investment-grade credit ratings, and it places restrictions on maturities and concentration by asset class and issuer.

We review our available-for-sale investments for other-than-temporary declines in fair value below our cost basis each quarter and whenever events or changes in circumstances indicate that the cost basis of an asset may not be recoverable. The evaluation is based on a number of factors, including the length of time and the extent to which the fair value has been below our cost basis, as well as adverse conditions related specifically to the security such as any changes to the credit rating of the security and the intent to sell or whether we will more likely than not be required to sell the security before recovery of its amortized cost basis. Based on our evaluation, we determined that our unrealized losses were not other-than-temporary at December 31, 2019. Our assessment of whether a security is other-than-temporarily impaired could change in the future based on new developments or changes in assumptions related to that particular security.

During the years ended December 31, 2019 and 2018, we had $81,700 and $0 realized gains on available-for-sale investments, respectively.

Equity Investments

We held investments in equity securities with readily determinable fair values of $26.0 million and $2.0 million at December 31, 2019 and 2018, respectively. These investments consist of mutual funds that invest primarily in tax free municipal bonds and treasury inflation protected securities.

Unrealized gains (losses) during 2019 and 2018 related to equity securities held at December 31, 2019 and 2018 are as follows:


	2019		2018
Net gains (losses) recognized during the year on equity securities	$	(101,674)	$	(16,233)
Less: net gains (losses) recognized during the year on equity securities sold during the year		—		—
Unrealized gains (losses) recognized during the year on equity securities still held at December 31, 2019 and 2018	$	(101,674)	$	16,233