One of the interesting ratios is the cost of a gallon as a percent of the price per barrel.

It has varied from of 5.20% in 1999 to the current ratio of approx 3.1% depending on where you live and the exact date of purchase.

Overall is has declined over the years, with some exceptions.

Since the tax is basically a fixed amount, the true gallon price percent may be more constant if the taxes were excluded.

I have tracked this ratio for 9 years based on each time I have purchased gas.