STOCKHOLDERS' EQUITY (Tables)

12 Months Ended

Dec. 31, 2018

Stock-based compensation expense recognized under ASC 718 was as follows:

	December 31,
	2018		2017		2016
General and administrative	$	263,431	$	127,378	$	133,904
Total stock-based compensation expense	$	263,431	$	127,378	$	133,904

The following table presents assumptions used to estimate the fair values of the stock options granted in the periods presented:

The summary of the stock options activity is as follows for year ended:

	Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value
Outstanding at January 1, 2016		297,000			20.14		3.10		10,561,380
Grants		-			-		-		-
Exercised		(45,000	)		8.79		-		1,554,100
Forfeitures or expirations		(20,000	)		29.21		-		-
Outstanding at December 31, 2017		232,000			21.56		2.52		5,050,990
Grants		81,500			51.42		-		-
Exercised		(138,000	)		18.63		-		3,720,149
Outstanding at December 31, 2018		175,500			37.73		6.33		4,014,235

Vested and expected to vest at December 31, 2018		175,500		$	37.73		6.33		4,014,235
Exercisable at December 31, 2018		86,500		$	24.84		3.22	$	3,093,460

The following table summarizes information relating to stock options by exercise price at December 31, 2018:

		Outstanding Shares						Exercisable Shares
Option Exercise Price		Number of Shares		Weighted Average Life (years)		Weighted Average Exercise Price		Number of Shares		Weighted Average Option Price		Weighted Average Life (years)
$	13.24 - 15.85		30,000		3.85	$	15.80		30,000	$	15.80		3.85
$	17.00 - 29.21		34,000		0.62		24.34		34,000		24.34		0.62
$	37.64 - 57.38		111,500		8.73		47.71		22,500		37.64		6.31
			175,500		6.33	$	37.73		86,500	$	24.84		3.22