We hear a lot these days about how gas and oil prices are at historical highs. But what we don't hear much about is how personal income is also at historical highs. Per-capita personal income has almost doubled in the last 15 years, from about $20,000 in March of 1993 to almost $40,000 in March of 2008 (personal income data available here, and population data available here).
The chart above (click to enlarge) shows the cost of 1,000 gallons of gas at average retail prices (data from EIA available here) as a percent of per-capita personal income, on a monthly basis from January 1980 through March 2008. Measured this way, gas prices through March 2008 aren't even close yet to the historical highs of the early 1980s, when 1,000 gallons of gas cost between 10-13% of per-capita personal income for 36 consecutive months, much higher than the 8.2% of per-capita income in March 2008.
The peak price of gas as a percent of income was in March 1981, when 1,000 gallons of gas cost 13% of per-capita disposable income. Gas today would have to reach a price of about $5.13 per gallon, before it would be an historical high adjusted for income.