Components of income tax expense were as follows (in thousands):
|
| | | | | | | | | | | | | |
| | | Year Ended December 31, |
| | | 2017 | | 2016 | | 2015 |
Current U.S. state | | $ | 942 |
| | $ | 704 |
| | $ | 479 |
|
Deferred U.S. state | | 393 |
| | 408 |
| | (228 | ) |
Income tax expense | | $ | 1,335 |
| | $ | 1,112 |
| | $ | 251 |
|
We are not a taxable entity for U.S. federal income tax purposes or for the majority of states that impose an income tax. Taxes on our net income generally are borne by our partners through the allocation of taxable income. Our income tax expense results from state laws that apply to entities organized as partnerships, specifically in the state of Texas. The difference between income tax expense recorded by us and income taxes computed by applying the statutory federal income tax rate (35 percent for all years presented) to income before income tax expense is due to the fact that the majority of our income is not subject to federal income tax at the entity level as described above.
As of December 31, 2017 and 2016, we had no liability reported for unrecognized tax benefits. We did not have any interest or penalties related to income taxes during the years ended December 31, 2017, 2016, and 2015.