Table:
|  |  | Year Ended March 31, |  |
| --- | --- | --- | --- |
|  | 2019 | 2018 | 2017 |
| Cost of sales (1) | $14.9 | $13.8 | $18.7 |
| Research and development | 72.0 | 42.5 | 46.8 |
| Selling, general and administrative | 62.3 | 36.9 | 62.6 |
| Special (income) charges and other, net | 17.2 | — | — |
| Pre-tax effect of share-based compensation | 166.4 | 93.2 | 128.1 |
| Income tax benefit | 35.5 | 28.3 | 44.2 |
| Net income effect of share-based compensation | $130.9 | $64.9 | $83.9 |
Paragraphs:
Note 16. Share-Based Compensation
Share-Based Compensation Expense
The following table presents the details of the Company's share-based compensation expense (in millions):
(1) During the year ended March 31, 2019, $17.2 million of share-based compensation expense was capitalized to inventory, and $14.9 million of previously capitalized share-based compensation expense in inventory was sold. During the year ended March 31, 2018, $11.9 million of share-based compensation expense was capitalized to inventory and $13.8 million of previously capitalized share-based compensation expense in inventory that was sold. During the year ended March 31, 2017, $11.3 million of share-based compensation expense was capitalized to inventory. The amount of sharebased compensation included in cost of sales during fiscal 2017 included $14.5 million of previously capitalized sharebased compensation expense in inventory was sold and $4.2 million of share-based compensation expense related to the Company's acquisition of Atmel that was not previously capitalized into inventory.
The amount of unearned share-based compensation currently estimated to be expensed in the remainder of fiscal 2020 through fiscal 2024 related to unvested share-based payment awards at March 31, 2019 is $253.4 million. The weighted average period over which the unearned share-based compensation is expected to be recognized is approximately 1.88 years.
Question:
What was the change in the cost of sales between 2017 and 2018?
Answer: 13.8-18.7 = -4.9