pre_text: 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.
table: Year ended December 31
table: 2019 2018 2017
table: Expected life (in years) 0.5 0.5 0.5
table: Volatility 36% - 37% 33% - 40% 29% - 37%
table: Risk-free interest rate 1.58 - 2.43% 1.76% - 2.50% 0.76% - 1.16%
table: Dividend yield - % - % - %
question: Analyse this data from a financial earnings document. What is the total shares issued under the ESPP between December 2017 to 2019?