our international crude oil production is relatively sweet and is generally sold in relation to the brent crude benchmark . the differential between wti and brent average prices widened significantly in 2011 and remained in 2012 in comparison to almost no differential in 2010 . natural gas 2013 a significant portion of our natural gas production in the lower 48 states of the u.s . is sold at bid-week prices or first-of-month indices relative to our specific producing areas . average henry hub settlement prices for natural gas were lower in 2012 than in recent years . a decline in average settlement date henry hub natural gas prices began in september 2011 and continued into 2012 . although prices stabilized in late 2012 , they have not increased appreciably . our other major natural gas-producing regions are e.g . and europe . in the case of e.g . our natural gas sales are subject to term contracts , making realizations less volatile . because natural gas sales from e.g . are at fixed prices , our worldwide reported average natural gas realizations may not fully track market price movements . natural gas prices in europe have been significantly higher than in the u.s . oil sands mining the osm segment produces and sells various qualities of synthetic crude oil . output mix can be impacted by operational problems or planned unit outages at the mines or upgrader . sales prices for roughly two-thirds of the normal output mix will track movements in wti and one-third will track movements in the canadian heavy sour crude oil marker , primarily wcs . in 2012 , the wcs discount from wti had increased , putting downward pressure on our average realizations . the operating cost structure of the osm operations is predominantly fixed and therefore many of the costs incurred in times of full operation continue during production downtime . per-unit costs are sensitive to production rates . key variable costs are natural gas and diesel fuel , which track commodity markets such as the canadian alberta energy company ( "aeco" ) natural gas sales index and crude oil prices , respectively . the table below shows average benchmark prices that impact both our revenues and variable costs. .

Table:
benchmark | 2012 | 2011 | 2010
wti crude oil ( dollars per bbl ) | $ 94.15 | $ 95.11 | $ 79.61
wcs ( dollars per bbl ) ( a ) | $ 73.18 | $ 77.97 | $ 65.31
aeco natural gas sales index ( dollars per mmbtu ) ( b ) | $ 2.39 | $ 3.68 | $ 3.89
wcs ( dollars per bbl ) ( a ) $ 73.18 $ 77.97 $ 65.31 aeco natural gas sales index ( dollars per mmbtu ) ( b ) $ 2.39 $ 3.68 $ 3.89 ( a ) monthly pricing based upon average wti adjusted for differentials unique to western canada .
( b ) monthly average day ahead index .
integrated gas our ig operations include production and marketing of products manufactured from natural gas , such as lng and methanol , in e.g .
world lng trade in 2012 has been estimated to be 240 mmt .
long-term , lng continues to be in demand as markets seek the benefits of clean burning natural gas .
market prices for lng are not reported or posted .
in general , lng delivered to the u.s .
is tied to henry hub prices and will track with changes in u.s .
natural gas prices , while lng sold in europe and asia is indexed to crude oil prices and will track the movement of those prices .
we have a 60 percent ownership in an lng production facility in e.g. , which sells lng under a long-term contract at prices tied to henry hub natural gas prices .
gross sales from the plant were 3.8 mmt , 4.1 mmt and 3.7 mmt in 2012 , 2011 and 2010 .
we own a 45 percent interest in a methanol plant located in e.g .
through our investment in ampco .
gross sales of methanol from the plant totaled 1.1 mmt , 1.0 mmt and 0.9 mmt in 2012 , 2011 and 2010 .
methanol demand has a direct impact on ampco 2019s earnings .
because global demand for methanol is rather limited , changes in the supply-demand balance can have a significant impact on sales prices .
world demand for methanol in 2012 has been estimated to be 49 mmt .
our plant capacity of 1.1 mmt is about 2 percent of world demand. .

Question: what was the difference in the average price of wti crude and wcs in 2012?
Answer: $ 20.97
Calculation: subtract(94.15, 73.18)