The consumer price index didn’t move a whole lot in March: The core rate, which excludes food and energy, was up just 0.1% over February. But dig down, and you’ll find that some components of the CPI moved a lot. Gasoline prices, for example, were up 6.5%. Meanwhile, apparel prices fell by 1.9% — the biggest one-month drop in 70 years. Month-to-month price fluctuations like those tell you just how difficult it is for the Bureau of Labor Statistics to measure inflation accurately. What consumers buy and how we buy it changes over time. Some products evolve quickly — think computers and smartphones — while others don’t change at all. Some prices vary seasonally, and sometimes the BLS changes the way it measures prices.

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