pre_text: Deferred income taxes reflect the net tax effects of temporary differences between the amounts of assets and liabilities for accounting purposes and the amounts used for income tax purposes. The components of the net deferred tax assets (liabilities) are as follows (amounts in millions): As of December 31, 2019, we had gross tax credit carryforwards of $191 million for state purposes. The tax credit carryforwards are included in Deferred tax assets net of unrealized tax benefits that would apply upon the realization of uncertain tax positions. In addition, we had foreign NOL carryforwards of $32 million at December 31, 2019, attributed mainly to losses in France which can be carried forward indefinitely. We evaluate deferred tax assets each period for recoverability. We record a valuation allowance for assets that do not meet the threshold of “more likely than not” to be realized in the future. To make that determination, we evaluate the likelihood of realization based on the weight of all positive and negative evidence available. As a result of the Closing Agreement, we received in 2018, we determined at that time that our remaining California research and development credit carryforwards (“CA R&D Credit”) no longer met the threshold of more likely than not to be realized in the future. As such, consistent with our position at December 31, 2018, we have established a full valuation allowance against our CA R&D Credit. For the year ended December 31, 2019, the valuation allowance related to our CA R&D Credit is $71 million. We will reassess this determination quarterly and record a tax benefit if and when future evidence allows for a partial or full release of this valuation allowance. As of December 31, 2017, we no longer consider the available cash balances related to undistributed earnings held outside of the U.S. by our foreign subsidiaries to be indefinitely reinvested.
table: , As of December 31,
table: 2019 2018
table: Deferred tax assets:
table: Allowance for sales returns and price protection $19 $25
table: Accrued expenses 28 26
table: Deferred revenue 119 136
table: Tax attributes carryforwards 93 81
table: Share-based compensation 54 69
table: Intangibles 1,289 43
table: U.S. deferred taxes on foreign earnings — 318
table: Capitalized software development expenses 67 —
table: Other 109 28
table: Deferred tax assets 1,778 726
table: Valuation allowance (181) (61)
table: Deferred tax assets, net of valuation allowance 1,597 665
table: Deferred tax liabilities:
table: Intangibles (142) (140)
table: Capitalized software development expenses — (57)
table: U.S. deferred taxes on foreign earnings (594) —
table: Other (73) (26)
table: Deferred tax liabilities (809) (223)
table: Net deferred tax assets $788 $442
question: Analyse this data from a financial earnings document. What was the change in net deferred tax assets between 2018 and 2019?