Table:
|  | Number of Shares | Weighted- Average Grant Date Fair Value |
| --- | --- | --- |
| Unvested shares at December 31, 2018 | 1,924 | $40.81 |
| Granted | 390 | 56.74 |
| Forfeited | (562) | 41.29 |
| Vested | — | — |
| Unvested shares at December 31, 2019 1 | 1,752 | $44.21 |
Paragraphs:
Performance-Based Restricted Stock Units
PRSU activity is summarized as follows (shares in thousands):
1 Assumes maximum achievement of the specified financial targets.
The weighted-average grant date fair value of PRSUs granted during the years ended December 31, 2019, 2018, and 2017 was $56.74, $40.53, and $41.73, respectively.
Unrecognized compensation expense related to unvested PRSUs was $16.9 million at December 31, 2019, which is expected to be recognized over a weighted-average period of 1.7 years.
Question:
What is the change in number of unvested shares between 2018 and 2019?
Answer: (1752-1924) = -172