Table:
|  | 2019 | 2018 | 2017 |
| --- | --- | --- | --- |
|  |  | (in thousands) |  |
| Beginning balance, as of January 1 | $43,395 | $36,263 | $38,958 |
| Additions: |  |  |  |
| Tax positions for current year | 1,322 | 4,716 | 8,208 |
| Tax positions for prior years | 8,043 | 2,626 | 199 |
| Reductions: |  |  |  |
| Tax positions for prior years | (31,397) | (153) | (10,573) |
| Expiration of statutes | (183) | (57) | (325) |
| Settlements with tax authorities | — | — | (204) |
| Ending balance, as of December 31 | $21,180 | $43,395 | $36,263 |
Paragraphs:
Teradyne’s gross unrecognized tax benefits for the years ended December 31, 2019, 2018 and 2017 were as follows:
Current year additions relate to federal and state research credits. Prior year additions primarily relate to stock-based compensation. Prior year reductions are primarily composed of federal and state reserves related to transfer pricing and research credits and resulted from the completion of the 2015 U.S. federal audit in the first quarter of 2019.
Of the $21.2 million of unrecognized tax benefits as of December 31, 2019, $12.7 million would impact the consolidated income tax rate if ultimately recognized. The remaining $8.5 million would impact deferred taxes if recognized.
Teradyne does not anticipate a material change in the balance of unrecognized tax benefits as of December 31, 2019 in the next twelve months.
Teradyne records all interest and penalties related to income taxes as a component of income tax expense. Accrued interest and penalties related to income tax items at December 31, 2019 and 2018 amounted to $1.4 million and $0.3 million, respectively. For the years ended December 31, 2019, 2018 and 2017, expense of $1.1 million, expense of $0.1 million and benefit of $0.1 million, respectively, was recorded for interest and penalties related to income tax items.
Teradyne is subject to U.S. federal income tax, as well as income tax in multiple state, local and foreign jurisdictions. As of December 31, 2019, all material state and local income tax matters have been concluded through 2013, all material federal income tax matters have been concluded through 2015 and all material foreign income tax matters have been concluded through 2011. However, in some jurisdictions, including the United States, operating losses and tax credits may be subject to adjustment until such time as they are utilized and the year of utilization is closed to adjustment.
As of December 31, 2019, Teradyne is not permanently reinvested with respect to the unremitted earnings of non-U.S. subsidiaries to the extent that those earnings exceed local statutory and operational requirements. Remittance of those earnings is not expected to result in material income tax.
Question:
What do Prior year additions primarily relate to?
Answer: stock-based compensation