item 7 . management 2019s discussion and analysis of financial condition and results of operations we are an international energy company with operations in the u.s. , canada , africa , the middle east and europe . our operations are organized into three reportable segments : 2022 e&p which explores for , produces and markets liquid hydrocarbons and natural gas on a worldwide basis . 2022 osm which mines , extracts and transports bitumen from oil sands deposits in alberta , canada , and upgrades the bitumen to produce and market synthetic crude oil and vacuum gas oil . 2022 ig which produces and markets products manufactured from natural gas , such as lng and methanol , in e.g . certain sections of management 2019s discussion and analysis of financial condition and results of operations include forward- looking statements concerning trends or events potentially affecting our business . these statements typically contain words such as "anticipates" "believes" "estimates" "expects" "targets" "plans" "projects" "could" "may" "should" "would" or similar words indicating that future outcomes are uncertain . in accordance with "safe harbor" provisions of the private securities litigation reform act of 1995 , these statements are accompanied by cautionary language identifying important factors , though not necessarily all such factors , which could cause future outcomes to differ materially from those set forth in forward-looking statements . for additional risk factors affecting our business , see item 1a . risk factors in this annual report on form 10-k . management 2019s discussion and analysis of financial condition and results of operations should be read in conjunction with the information under item 1 . business , item 1a . risk factors and item 8 . financial statements and supplementary data found in this annual report on form 10-k . spin-off downstream business on june 30 , 2011 , the spin-off of marathon 2019s downstream business was completed , creating two independent energy companies : marathon oil and mpc . marathon stockholders at the close of business on the record date of june 27 , 2011 received one share of mpc common stock for every two shares of marathon common stock held . a private letter tax ruling received in june 2011 from the irs affirmed the tax-free nature of the spin-off . activities related to the downstream business have been treated as discontinued operations in 2011 and 2010 ( see item 8 . financial statements and supplementary data 2013 note 3 to the consolidated financial statements for additional information ) . overview 2013 market conditions exploration and production prevailing prices for the various grades of crude oil and natural gas that we produce significantly impact our revenues and cash flows . the following table lists benchmark crude oil and natural gas price annual averages for the past three years. .

Table:
benchmark | 2012 | 2011 | 2010
wti crude oil ( dollars per bbl ) | $ 94.15 | $ 95.11 | $ 79.61
brent ( europe ) crude oil ( dollars per bbl ) | $ 111.65 | $ 111.26 | $ 79.51
henry hub natural gas ( dollars per mmbtu ) ( a ) | $ 2.79 | $ 4.04 | $ 4.39
henry hub natural gas ( dollars per mmbtu ) ( a ) $ 2.79 $ 4.04 $ 4.39 ( a ) settlement date average .
liquid hydrocarbon 2013 prices of crude oil have been volatile in recent years , but less so when comparing annual averages for 2012 and 2011 .
in 2011 , crude prices increased over 2010 levels , with increases in brent averages outstripping those in wti .
the quality , location and composition of our liquid hydrocarbon production mix will cause our u.s .
liquid hydrocarbon realizations to differ from the wti benchmark .
in 2012 , 2011 and 2010 , the percentage of our u.s .
crude oil and condensate production that was sour averaged 37 percent , 58 percent and 68 percent .
sour crude contains more sulfur and tends to be heavier than light sweet crude oil so that refining it is more costly and produces lower value products ; therefore , sour crude is considered of lower quality and typically sells at a discount to wti .
the percentage of our u.s .
crude and condensate production that is sour has been decreasing as onshore production from the eagle ford and bakken shale plays increases and production from the gulf of mexico declines .
in recent years , crude oil sold along the u.s .
gulf coast has been priced at a premium to wti because the louisiana light sweet benchmark has been tracking brent , while production from inland areas farther from large refineries has been at a discount to wti .
ngls were 10 percent , 7 percent and 6 percent of our u.s .
liquid hydrocarbon sales in 2012 , 2011 and 2010 .
in 2012 , our sales of ngls increased due to our development of u.s .
unconventional liquids-rich plays. .

Question: between 2012 and 2011 , what was the change in the percentage of crude oil and condensate production that was sour?
Answer: -21
Calculation: subtract(37, 58)