because of the low fuel taxes, the retail price of gasoline in the us is subject to greater changes (than outside the us) when calculated as a percentage of cost-per-unit. from 1998 to 2004, the price of gasoline was between $1 and $2 usd per u.s. gallon. after 2004, the price increased until the average gas price reached a high of $4.11 per u.s. gallon in mid-2008, then dropped approximately $2.60 per u.s. gallon as of september 2009. recently, the u.s. has experienced an upswing in gas prices of 13.51% from jan 31st to march 7, 2011.