Sometime soon, the price of a barrel of sweet light crude oil will hit $100. One hundred dollars a barrel is one of those benchmark numbers that reporters use to get stories approved by their editors, like the upcoming 80th anniversary of the production of the first Milk Dud.

One hundred dollars is not a number with a lot of meaning — not much different than $99.90 — unless you put it into context. The usual method is to translate it into the price of a gallon of gas.

For me, an apt comparison is how much I paid for gas when I owned my first internal combustion machine, when I was 12. I call this the El Tigre Index.

So let's compare. I bought my first gallon of gasoline in 1970, for 29.9 cents. It was fuel for my Arctic Cat El Tigre mini-bike. Thus the Index was born. (Gas may have cost less elsewhere, but the owners of the three gas stations in my hometown regularly conspired to fix prices, and they were undercutting the pumps in the next town up the highway.)

It cost me barely 75 cents to fill the tank of my leopard-skin-seat El Tigre. But I dug deep for that gas because my annual income was $36 — $4 each week for 12 weeks worth of mowing Mr. Hach's endless lawn.

I had paid the equivalent of $1.59 in 2006 dollars for a gallon, or nearly $4 for a fill-up, according to the Consumer Price Index. The average gas price as of the end of the first week of November 2007, according to the U.S. Department of Energy, was $3.01 per gallon.

If I filled the tank today — it's still in Dad's garage — it would cost a bit more than $7.50.

According to the El Tigre Index, the burden of filling up that gas tank today — as we near that magical, meaningless $100 mark — is about 1.9 times as much as in 1970.

Fortunately, Milk Duds are still a bargain.