In The Wall Street Journal’s latest poll of swing states, 74% of respondents said inflation has moved in the wrong direction in the past year. This assessment, which holds across all seven states, is startling, sobering—and simply not true. I’m not stating an opinion. This isn’t something on which reasonable people can disagree. If hard economic data count for anything, we can say unambiguously that inflation has moved in the right direction in the past year. In the 12 months through February, inflation, according to the century-old consumer-price index, was 3.2%, compared with 6% a year earlier. Use a slightly...