Table:
|  |  | Year Ended December 31, |  |
| --- | --- | --- | --- |
|  | 2019 | 2018 | 2017 |
| Tax at federal statutory rate | 21.0 % | 21.0 % | 35.0 % |
| State taxes, net of federal effect | (0.3) | (0.1) | (5.4) |
| Foreign rate differential | (6.0) | (3.9) | (9.3) |
| Tax credits | 1.6 | 6.3 | 4.1 |
| Domestic production activities deduction | — | — | (3.5) |
| Stock-based compensation | (1.0) | (4.9) | (5.3) |
| Change in prior year reserves | (1.5) | (0.1) | (2.0) |
| Change in valuation allowance | (13.4) | (15.2) | (35.2) |
| Effect of change in tax rate due to Tax Act | — | — | (23.4) |
| Other (1) | (4.2) | (4.0) | 2.6 |
| Effective tax rate | (3.8)% | (0.9)% | (42.4)% |
Paragraphs:
The reconciliation of the Company’s effective tax rate to the statutory federal rate is as follows:
(1) For the years ended December 31, 2019 and December 31, 2018, this is inclusive of (3.4%) and (3.8%) impact, respectively, that is primarily related to the change in uncertain tax positions.
For 2019, the Company recorded an expense for income taxes of $11.6 million, resulting in an effective tax rate of (3.8)%. The effective tax rate is different than the U.S. statutory federal tax rate primarily due to stock-based compensation expense following the decision in Altera Corp v. Commissioner by the U.S. Court of Appeals for the Ninth Circuit discussed below, the full valuation allowance on the Company's U.S. deferred tax assets, the mix of income/losses among the Company’s foreign jurisdictions, and pretax losses in jurisdictions for which no tax benefit will be recognized.
Question:
What is the difference in tax credits between 2018 and 2019?
Answer: 6.3-1.6 = 4.7