CARACAS, Venezuela—Prices here are doubling every few weeks, confounding cash-strapped Venezuelans who are scrambling to find a way to pay for basic transactions.

A Jesuit priest, Alfredo Infante, has turned to a novel formula to keep up with skyrocketing costs: He meticulously tracks the price of the humble egg. Six months ago, donations from one Sunday mass could buy 30 eggs for church events, he said. Now, he needs more than 50 Sundays to buy the same number of eggs.

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