2019
2018
U.S. net operating loss carryforwards
2,894,000
2,627,000
Stock compensation
784,000
359,000
Canadian Provincial income tax losses
29,000
56,000
Canadian Provincial scientific investment tax credits
(4,000)
-
3,703,000
3,042,000
Valuation allowance
(3,703,000)
(3,042,000)
Net deferred tax assets
-
-
the tax effects of temporary differences that give rise to the company ’ s deferred tax assets and liabilities are as follows : .
as of december 31 2019 and 2018 the company had federal net operating loss carryforwards - “ nol ” of approximately $ 7161000 and $ 6617000 respectively .
the losses expire beginning in 2024 .
the company has not performed a detailed analysis to determine whether an ownership change under irc section 382 has occurred .
the effect of an ownership change would be the imposition of annual limitation on the use of nol carryforwards attributable to periods before the change any limitation may result in expiration of a portion of the nol before utilization .
as of december 31 2019 and 2018 the company had state and local net operating loss carryforwards of approximately $ 7153000 and $ 6609000 respectively to reduce future state tax liabilities also through 2035 .
as of december 31 2019 and 2018 the company had canadian nol of approximately $ 1111000 and $ 1070000 respectively .
the canadian losses expire in stages beginning in 2026 .
as of december 31 2019 and 2018 the company also has unclaimed canadian federal scientific research and development investment tax credits which are available to reduce future federal taxes payable of approximately $ 0 and $ 0 respectively .
as of december 31 2019 and 2018 the company had canadian nol of approximately $ 1111000 and $ 1070000 respectively .
the canadian losses expire in stages beginning in 2026 .
as of december 31 2019 and 2018 the company also has unclaimed canadian federal scientific research and development investment tax credits which are available to reduce future federal taxes payable of approximately $ 0 and $ 0 respectively .
as of december 31 2019 and 2018 the company had canadian nol of approximately $ 1111000 and $ 1070000 respectively .
the canadian losses expire in stages beginning in 2026 .
as of december 31 2019 and 2018 the company also has unclaimed canadian federal scientific research and development investment tax credits which are available to reduce future federal taxes payable of approximately $ 0 and $ 0 respectively .
as of december 31 2019 and 2018 the company had canadian nol of approximately $ 1111000 and $ 1070000 respectively .
the canadian losses expire in stages beginning in 2026 .
as of december 31 2019 and 2018 the company also has unclaimed canadian federal scientific research and development investment tax credits which are available to reduce future federal taxes payable of approximately $ 0 and $ 0 respectively .
as a result of losses and uncertainty of future profit the net deferred tax asset has been fully reserved .
the net change in the valuation allowance during the years ended december 31 2019 and 2018 was an increase of $ 661000 and $ 457000 respectively .
foreign earnings are assumed to be permanently reinvested .
u .
s .
federal income taxes have not been provided on undistributed earnings of our foreign subsidiary .
the company recognizes interest and penalties related to uncertain tax positions in selling general and administrative expenses .
the company has not identified any uncertain tax positions requiring a reserve as of december 31 2019 and 2018 .
the company is required to file u .
s .
federal and state income tax returns .
these returns are subject to audit by tax authorities beginning with the year ended december 31 2014 .

Question: What is the difference in valuation allowance between 2018 and 2019?
Answer: 661000