Weighted average exercise price of options, expected to vest (in usd per share)

  
The following table summarizes the Company’s total unrecognized compensation cost related to stock based compensation as of December 31, 2021 (cost in thousands): 

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
|  |  | UnrecognizedCompensationCost |  | Weighted AveragePeriod of ExpenseRecognition(in Years) |
| Stock options |  | $ | 80,305  |  |  | 1.60 |
| Restricted stock |  | 28,349  |  |  | 0.76 |
| Total |  | $ | 108,654  |  |  |  |

Stock OptionsThe following summarizes the changes in the number of shares of common stock under option for the following periods (shares and aggregate intrinsic value in thousands): 

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
|  |  | Shares |  | WeightedAverageExercisePrice |  | OptionsExercisableat End ofYear |  | WeightedAverageExercisePrice ofExercisableOptions |  | WeightedAverage FairValue ofOptionsGranted Duringthe Year |  | AggregateIntrinsicValue |
| Outstanding at December 31, 2018 |  | 7,616  |  |  | $ | 117.58  |  |  | 5,174  |  |  | $ | 98.39  |  |  |  |  | $ | 518,954  |  |
| Granted |  | 431  |  |  | 244.35  |  |  |  |  |  |  | $ | 57.99  |  |  |  |
| Exercised |  | (1,482) |  |  | 115.53  |  |  |  |  |  |  |  |  | 255,242  |  |
| Forfeited |  | (302) |  |  | 167.35  |  |  |  |  |  |  |  |  |  |
| Outstanding at December 31, 2019 |  | 6,263  |  |  | 124.38  |  |  | 5,137  |  |  | 109.03  |  |  |  |  | 1,022,860  |  |
| Granted |  | 503  |  |  | 215.36  |  |  |  |  |  |  | $ | 53.18  |  |  |  |
| Exercised |  | (1,681) |  |  | 80.84  |  |  |  |  |  |  |  |  | 322,823  |  |
| Forfeited |  | (121) |  |  | 194.61  |  |  |  |  |  |  |  |  |  |
| Outstanding at December 31, 2020 |  | 4,964  |  |  | 146.69  |  |  | 3,994  |  |  | 130.37  |  |  |  |  | 626,107  |  |
| Granted |  | 1,097  |  |  | 261.85  |  |  |  |  |  |  | $ | 72.84  |  |  |  |
| Exercised |  | (592) |  |  | 82.50  |  |  |  |  |  |  |  |  | 83,686  |  |
| Forfeited |  | (22) |  |  | 230.14  |  |  |  |  |  |  |  |  |  |
| Outstanding at December 31, 2021 |  | 5,447  |  |  | $ | 176.52  |  |  | 3,798  |  |  | $ | 145.18  |  |  |  |  | $ | 257,707  |  |
| Expected to vest at December 31, 2021 |  | 1,648  |  |  | $ | 248.75  |  |  |  |  |  |  |  |  |  |

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