welltower inc . notes to consolidated financial statements is no longer present ( and additional weight may be given to subjective evidence such as our projections for growth ) . the valuation allowance rollforward is summarized as follows for the periods presented ( in thousands ) : year ended december 31 , 2017 2016 2015 .
for the years ended december 31 2017 , 2016 , and 2015 , what was the average beginning balance in millions?
as a result of certain acquisitions , we are subject to corporate level taxes for any related asset dispositions that may occur during the five-year period immediately after such assets were owned by a c corporation ( 201cbuilt-in gains tax 201d ) . the amount of income potentially subject to this special corporate level tax is generally equal to the lesser of ( a ) the excess of the fair value of the asset over its adjusted tax basis as of the date it became a reit asset , or ( b ) the actual amount of gain . some but not all gains recognized during this period of time could be offset by available net operating losses and capital loss carryforwards . during the year ended december 31 , 2016 , we acquired certain additional assets with built-in gains as of the date of acquisition that could be subject to the built-in gains tax if disposed of prior to the expiration of the applicable ten-year period . we have not recorded a deferred tax liability as a result of the potential built-in gains tax based on our intentions with respect to such properties and available tax planning strategies . under the provisions of the reit investment diversification and empowerment act of 2007 ( 201cridea 201d ) , for taxable years beginning after july 30 , 2008 , the reit may lease 201cqualified health care properties 201d on an arm 2019s-length basis to a trs if the property is operated on behalf of such subsidiary by a person who qualifies as an 201celigible independent contractor . 201d generally , the rent received from the trs will meet the related party rent exception and will be treated as 201crents from real property . 201d a 201cqualified health care property 201d includes real property and any personal property that is , or is necessary or incidental to the use of , a hospital , nursing facility , assisted living facility , congregate care facility , qualified continuing care facility , or other licensed facility which extends medical or nursing or ancillary services to patients . we have entered into various joint ventures that were structured under ridea . resident level rents and related operating expenses for these facilities are reported in the consolidated financial statements and are subject to federal , state and foreign income taxes as the operations of such facilities are included in a trs . certain net operating loss carryforwards could be utilized to offset taxable income in future years . given the applicable statute of limitations , we generally are subject to audit by the internal revenue service ( 201cirs 201d ) for the year ended december 31 , 2014 and subsequent years . the statute of limitations may vary in the states in which we own properties or conduct business . we do not expect to be subject to audit by state taxing authorities for any year prior to the year ended december 31 , 2011 . we are also subject to audit by the canada revenue agency and provincial authorities generally for periods subsequent to may 2012 related to entities acquired or formed in connection with acquisitions , and by the u.k . 2019s hm revenue & customs for periods subsequent to august 2012 related to entities acquired or formed in connection with acquisitions . at december 31 , 2017 , we had a net operating loss ( 201cnol 201d ) carryforward related to the reit of $ 448475000 . due to our uncertainty regarding the realization of certain deferred tax assets , we have not recorded a deferred tax asset related to nols generated by the reit . these amounts can be used to offset future taxable income ( and/or taxable income for prior years if an audit determines that tax is owed ) , if any . the reit will be entitled to utilize nols and tax credit carryforwards only to the extent that reit taxable income exceeds our deduction for dividends paid . the nol carryforwards generated through december 31 , 2017 will expire through 2036 . beginning with tax years after december 31 , 2017 , the tax cuts and jobs act ( 201ctax act 201d ) eliminates the carryback period , limits the nols to 80% ( 80 % ) of taxable income and replaces the 20-year carryforward period with an indefinite carryforward period. .