3. STOCK-BASED COMPENSATION

We measure stock-based compensation expense based on the grant date fair value of the awards, which is then recognized over the period which service is required to be provided. We estimate the value of our stock option awards on the date of grant using the Black-Scholes option pricing model (“Black-Scholes”) and amortize that cost over the expected term of the grant. We recognized $146,433 and $115,307 in stock-based compensation expense for the three months ended June 30, 2020 and 2019. We recognized $196,272 and $170,062 in stock- based compensation expense for the six months ended June 30, 2020 and 2019, respectively. We issued 2,130,000 stock options to employees, consultants and directors during the six months ended June 30, 2020 and 2,415,000 stock options to employees, consultants and directors during the six months ended June 30, 2019. We used the following forward-looking range of assumptions to value the stock options issue in 2020 and 2019:


	2020		2019
Dividend yield	0.0	%	0.0	%
Risk-free rate of return	0.33	%	2.15	%
Expected life in years	5.88		5.88
Volatility	74.57	%	93.59	%
Forfeiture rate	2.6	%	2.6	%

A summary of the Company’s stock options for the six months ended June 30, 2020 is as follows:


				Weighted
				Average
		Weighted		Remaining
	Number of	Average		Contractual		Aggregate
	Shares	Exercise Price		Life		Intrinsic Value
Options Outstanding, December 31, 2019	9,821,250	$	0.28
Granted	2,130,000	$	0.30
Exercised	—	$	—
Forfeited	—	$	—
Options Outstanding, June 30, 2020	11,951,250	$	0.28	5.9	years	$	813,600
Vested and unvested but expected to vest, June 30, 2020	11,784,785	$	0.28	5.9	years	$	802,268
Exercisable at June 30, 2020	8,093,750	$	0.30	4.4	years	$	550,550

The average expected life was determined using historical data. We expect to recognize the compensation cost related to non-vested options as of June 30, 2020 of $558,474 over the weighted average remaining recognition period of 1.57 years.