CARACAS—On monthly trips to his native Venezuela, Miguel Octavio heads to the same restaurant for the cornmeal cakes he enjoyed as a boy known as arepas, which are a staple here. The price, however, is never the same.

Over nine months, the Miami-based financial analyst and blogger has recorded a fourfold increase in what he calls his Hyperinflated Arepa Index, a yardstick he created to trace soaring consumer prices in this economically crippled country.

President Nicolás Maduro’s government stopped publishing monthly inflation data last December when the level hit 68% annually, the world’s highest. With the Venezuelan economy worsening and the ruling party facing tough congressional elections this December, the central bank hasn’t reported inflation, balance-of-payments or gross-domestic-product figures all year.

That has prompted economists and analysts like Mr. Octavio to compile their own indicators, basing calculations on everything from anecdotal evidence to federal tax revenue to banking-sector loans.

“It’s trying to fill that gap,” Mr. Octavio said. “And, of course, it took over my life, because I had to update the blog every time to keep up.”