supplementary information on oil and gas producing activities ( unaudited ) 2018 proved reserves decreased by 168 mmboe primarily due to the following : 2022 revisions of previous estimates : increased by 84 mmboe including an increase of 108 mmboe associated with the acceleration of higher economic wells in the u.s . resource plays into the 5-year plan and an increase of 15 mmboe associated with wells to sales that were additions to the plan , partially offset by a decrease of 39 mmboe due to technical revisions across the business . 2022 extensions , discoveries , and other additions : increased by 102 mmboe primarily in the u.s . resource plays due to an increase of 69 mmboe associated with the expansion of proved areas and an increase of 33 mmboe associated with wells to sales from unproved categories . 2022 production : decreased by 153 mmboe . 2022 sales of reserves in place : decreased by 201 mmboe including 196 mmboe associated with the sale of our subsidiary in libya , 4 mmboe associated with divestitures of certain conventional assets in new mexico and michigan , and 1 mmboe associated with the sale of the sarsang block in kurdistan . 2017 proved reserves decreased by 647 mmboe primarily due to the following : 2022 revisions of previous estimates : increased by 49 mmboe primarily due to the acceleration of higher economic wells in the bakken into the 5-year plan resulting in an increase of 44 mmboe , with the remainder being due to revisions across the business . 2022 extensions , discoveries , and other additions : increased by 116 mmboe primarily due to an increase of 97 mmboe associated with the expansion of proved areas and wells to sales from unproved categories in oklahoma . 2022 purchases of reserves in place : increased by 28 mmboe from acquisitions of assets in the northern delaware basin in new mexico . 2022 production : decreased by 145 mmboe . 2022 sales of reserves in place : decreased by 695 mmboe including 685 mmboe associated with the sale of our canadian business and 10 mmboe associated with divestitures of certain conventional assets in oklahoma and colorado . see item 8 . financial statements and supplementary data - note 5 to the consolidated financial statements for information regarding these dispositions . 2016 proved reserves decreased by 67 mmboe primarily due to the following : 2022 revisions of previous estimates : increased by 63 mmboe primarily due to an increase of 151 mmboe associated with the acceleration of higher economic wells in the u.s . resource plays into the 5-year plan and a decrease of 64 mmboe due to u.s . technical revisions . 2022 extensions , discoveries , and other additions : increased by 60 mmboe primarily associated with the expansion of proved areas and new wells to sales from unproven categories in oklahoma . 2022 purchases of reserves in place : increased by 34 mmboe from acquisition of stack assets in oklahoma . 2022 production : decreased by 144 mmboe . 2022 sales of reserves in place : decreased by 84 mmboe associated with the divestitures of certain wyoming and gulf of mexico assets . changes in proved undeveloped reserves as of december 31 , 2018 , 529 mmboe of proved undeveloped reserves were reported , a decrease of 17 mmboe from december 31 , 2017 . the following table shows changes in proved undeveloped reserves for 2018 : ( mmboe ) .
what percentage of 2018 ending balance of proven undeveloped reserves consisted ofextensions discoveries and other additions?
.