Gasoline
Here is a paragraph from my journal, dated 12 March 1979:
Gasoline is constantly increasing in cost: 68.9¢ now; about a year ago, 56.9¢. About all I can do to overcome the price is to always drive gas-efficient vehicles and avoid extraneous outings.
I added the following comment 20 years later (on 12 March 1999):
The price for regular unleaded gasoline—the cheapest grade—is now 91.9¢ per gallon at my local Texaco station. I have seen it as high as $1.20 per gallon during the past twenty years.
I’m more surprised by the price nine years ago than I am by the price 29 years ago.