December 31, | |||||||||||||||||||||
2015 | 2016 | 2017 | |||||||||||||||||||
Number | WAEP | Number | WAEP | Number | WAEP | ||||||||||||||||
Outstanding at January 1, | 6,455,048 | $ | 3.93 | 7,428,931 | $ | 3.58 | 7,177,500 | $ | 3.55 | ||||||||||||
Granted during the year | 1,321,850 | $ | 1.74 | 643,350 | $ | 2.07 | 230,000 | $ | 3.39 | ||||||||||||
Forfeited during the year | (325,967 | ) | $ | 3.01 | (317,880 | ) | $ | 2.97 | (336,365 | ) | $ | 4.75 | |||||||||
Exercised during the year(1) | (22,000 | ) | $ | 1.70 | (187,901 | ) | $ | 1.53 | (431,790 | ) | $ | 2.28 | |||||||||
Expired during the year | — | (389,000 | ) | $ | 3.12 | (441,497 | ) | $ | 3.25 | ||||||||||||
Outstanding at period end | 7,428,931 | $ | 3.58 | 7,177,500 | $ | 3.55 | 6,197,848 | $ | 3.59 | ||||||||||||
Of which, warrants for consultants equivalent to employees | 369,798 | $ | 3.38 | 404,798 | $ | 3.23 | 151,500 | $ | 3.29 | ||||||||||||
Exercisable at period end | 4,691,741 | $ | 4.69 | 5,049,015 | $ | 4.28 | 4,900,052 | $ | 3.90 | ||||||||||||
Of which, warrants for consultants equivalent to employees | 360,798 | $ | 3.44 | 360,215 | $ | 3.41 | 131,917 | $ | 3.51 | ||||||||||||
(1) | The weighted average share estimated fair value at the dates of exercise of these options was $3.49 in 2017, $2.21 in 2016 and $1.73 in 2015. |