Table:
|  |  | Year ended December 31 |  |
| --- | --- | --- | --- |
|  | 2019 | 2018 | 2017 |
| Expected life (in years) | 0.5 | 0.5 | 0.5 |
| Volatility | 36% - 37% | 33% - 40% | 29% - 37% |
| Risk-free interest rate | 1.58 - 2.43% | 1.76% - 2.50% | 0.76% - 1.16% |
| Dividend yield | - % | - % | - % |
Paragraphs:
The fair value of the option component of the ESPP shares was estimated at the grant date using the Black-Scholes option pricing model with the following weighted
average assumptions:
The Company issued 266 shares, 231 shares and 183 shares under the ESPP in the years ended December 31, 2019, 2018 and 2017, respectively, at a weighted average
exercise price per share of $86.51, $77.02, and $73.02, respectively. As of December 31, 2019, the Company expects to recognize $3,531 of the total unamortized compensation cost
related to employee purchases under the ESPP over a weighted average period of 0.37 years.
Question:
What is the expected life (in years) of the option component of the ESPP shares in each of the years ended December 31, 2019?
Answer: 0.5, 0.5, 0.5