pre_text: Utilization of the net operating loss and tax credit carry forwards are subject to an annual limitation due to the ownership percentage change limitations provided by the Internal Revenue Code of 1986 and similar state provisions. The annual limitation may result in the expiration of the net operating loss before utilization. The Company does not expect the limitation to result in a reduction in the total amount utilizable. The Company is subject to income taxes in the U.S. (federal and state) and numerous foreign jurisdictions. Significant judgment is required in evaluating the Company’s tax positions and determining its provision for income taxes. During the ordinary course of business, there are many transactions and calculations for which the ultimate tax determination is uncertain. The Company establishes reserves for tax-related uncertainties based on estimates of whether, and the extent to which, additional taxes will be due. These reserves are established when the Company believes that certain positions might be challenged despite its belief that its tax return positions are fully supportable. The Company adjusts these reserves in light of changing facts and circumstances, such as the outcome of tax audits. The provision for income taxes includes the impact of reserve provisions and changes to reserves that are considered appropriate. As of December 31, 2019 and 2018, the Company had $67.0 million and $41.2 million of unrecognized tax benefits, respectively. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands): At December 31, 2019, the total amount of gross unrecognized tax benefits was $67.0 million, of which $31.9 million would affect the Company’s effective tax rate if recognized. The Company does not have any tax positions as of December 31, 2019 for which it is reasonably possible the total amount of gross unrecognized tax benefits will increase or decrease within the following 12 months. The Company’s policy is to record interest and penalties related to unrecognized tax benefits as income tax expense. As of December 31, 2019 and 2018, respectively, the Company has accrued $5.2 million and $3.1 million related to interest and penalties, respectively. The material jurisdictions in which the Company is subject to potential examination include the United States and Ireland. The Company believes that adequate amounts have been reserved for these jurisdictions. For the United States, the Company is currently under examination by the Internal Revenue Service ("IRS") for fiscal 2015 to 2017. For state and non-U.S. tax returns, the Company is generally no longer subject to tax examinations for years prior to 2014.
table: December 31,
table: 2019 2018 2017
table: Balance at beginning of year $41,198 $29,938 $35,584
table: Reductions based on tax positions related to prior year (207) (820) (6,335)
table: Additions based on tax positions related to prior year 9,562 263 108
table: Additions based on tax positions related to current year 16,517 11,860 9,289
table: Reductions due to tax authorities’ settlements — (43) (8,603)
table: Reductions due to expiration of statutes of limitation (45) — (105)
table: Balance at end of year $67,025 $41,198 $29,938
question: Analyse this data from a financial earnings document. What is the average additions based on tax positions related to prior year from 2017-2019?