Table:
|  | Year Ended | Year Ended |
| --- | --- | --- |
|  | December 31, 2018 | December 31, 2019 |
| United States federal statutory rate | 21.00% | 21.00% |
| State taxes, net of federal benefit | 1.99% | (0.01)% |
| Valuation allowance | (21.96)% | (24.33)% |
| Cumulative effect of accounting change | — | 2.07% |
| R&D Credit | 1.34% | 1.53% |
| Other | (0.38)% | (0.27)% |
| Effective income tax rate | 1.99% | (0.01)% |
Paragraphs:
Effective Income Tax Rate
A reconciliation of the United States federal statutory income tax rate to our effective income tax rate is as follows:
In 2019 and 2018 we had pre-tax losses of $19,573 and $25,403, respectively, which are available for carry forward to offset future taxable income. We made determinations to provide full valuation allowances for our net deferred tax assets at the end of 2019 and 2018, including NOL carryforwards generated during the years, based on our evaluation of positive and negative evidence, including our history of operating losses and the uncertainty of generating future taxable income that would enable us to realize our deferred tax.
Question:
What was the change in the United States federal statutory rate between 2018 and 2019?
Answer: 21.00 - 21.00  = 0