February 10, 2012
Short-term measures of real family income are driven primarily by sampling error and erratic movements in the consumer price index. The latter is mostly due to fluctuations in energy prices.
This is the reason that most economists, unlike USA Today, would not take seriously a report showing a large gain in median family income in the last four months of 2011. The main reason for the sharp rise in income shown in this report is likely the sharp drop in the consumer price index over this period.
It is more useful to report these data over longer periods of time so that random fluctuations play less of a role. Given the vast amount of material that is available for free on the web, it is especially difficult to understand why USA Today would place so much emphasis on a newly produced report that is being sold for $20 each.
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