Table:
| As of | 2019 | 2018 |
| --- | --- | --- |
| Deferred tax assets |  |  |
| Net operating loss and tax credit carryforwards | $1,045 | $1,417 |
| Accrued salaries, wages, and benefits | 122 | 163 |
| Property, plant, and equipment | 80 | — |
| Other | 110 | 115 |
| Gross deferred tax assets | 1,357 | 1,695 |
| Less valuation allowance | (277) | (228) |
| Deferred tax assets, net of valuation allowance | 1,080 | 1,467 |
| Deferred tax liabilities |  |  |
| Product and process technology | (138) | (62) |
| Property, plant, and equipment | — | (173) |
| Other | (109) | (213) |
| Deferred tax liabilities | (247) | (448) |
| Net deferred tax assets | $833 | $1,019 |
| Reported as |  |  |
| Deferred tax assets | $837 | $1,022 |
| Deferred tax liabilities (included in other noncurrent liabilities) | (4) | (3) |
| Net deferred tax assets | $833 | $1,019 |
Paragraphs:
Deferred income taxes reflect the net tax effects of temporary differences between the bases of assets and liabilities for financial reporting and income tax purposes as well as carryforwards. Deferred tax assets and liabilities consist of the following:
We assess positive and negative evidence for each jurisdiction to determine whether it is more likely than not that existing deferred tax assets will be realized. As of August 29, 2019, and August 30, 2018, we had a valuation allowance of $277 million and $228 million, respectively, against our net deferred tax assets, primarily related to net operating loss carryforwards in Japan. Changes in 2019 in the valuation allowance were due to adjustments based on management's assessment of tax credits and net operating losses that are more likely than not to be realized.
Question:
What caused the change in valuation allowance in 2019?
Answer: adjustments based on management's assessment of tax credits and net operating losses that are more likely than not to be realized