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Stock-Based Compensation (Tables)
9 Months Ended
Sep. 30, 2019
Share-based Payment Arrangement [Abstract]  
Schedule of weighted average assumptions
The weighted average assumptions used in the Black-Scholes model for option grants to employees and directors are presented below:
 
Three Months Ended September 30,
 
Nine Months Ended September 30,
 
2019
 
2018
 
2019
 
2018
Risk-free interest rate
1.75%
 
2.86%
 
2.43%
 
2.73%
Expected volatility
65%
 
71%
 
70%
 
72%
Expected life in years
6.1
 
6.1
 
6.2
 
6.2
Dividend yield