Median Household Income Growth: Deflating The American Dream

 | Sep 17, 2014 01:11AM ET

What is the single best indicator of the Income and Poverty in the United States: 2013 . Last year the median (middle) household income was $51,939 -- a 1.8% year-over-year increase that shrinks to 0.3% when adjusted for inflation. Let's put the new release into a larger historical context.

My study of the Census Bureau's historical data shows a 627% growth in median household incomes from 1967 through 2013. The ride has been bumpy, but it equates to a 4.41% annualized growth rate. Sounds impressive, but if you adjust for inflation using the Census Bureau's method, that nominal 627% total growth shrinks to about 19%, a "real" annualized growth rate of 0.38%.

But if we dig a bit deeper into the method of inflation adjustment, the American Dream looks more like an illusion, as in "money illusion ".

Median Household Incomes: Monthly Update . The Sentier Research findings are based on Census Bureau (CB) data and adjusted for inflation using the Bureau of Labor Statistics (BLS) Consumer Price Index for Urban Consumers (CPI-U), which most people, including the BLS, commonly abbreviate as the "CPI". However, the CB's own annual data series for household income, which reaches back to 1967, uses a different index to "deflate" the nominal income data. The CB researchers adjust using the little-known CPI-U-RS (RS stands for "research series") as the deflator for their annual data.

The BLS website has slender information about this index. A site search turns up PDF file with the index from 1977 through 2013.

Obviously the CB has a version of the annual CPI-U-RS back to 1967, the starting year for their household income series. I have not found the pre-1978 annual CPI-U-RS data at either the CB or BLS website. However, we can constuct this index from the CB's latest annual data from 1967-2013 in Table H-5 linkable from their Historical Household Income Tables .

The Deflator Difference

A price index, such as the CPI or the BEA's PCE price index, provides the data we need to "deflate" nominal dollar values to their real purchasing power over time. And even in stable economies, over long periods of time, the "money illusion" of nominal values can be substantial, as the chart above painfully illustrates.

As I mentioned earlier, Sentier Research uses the more familiar CPI as the deflator for computing their real household income data series. Does the deflator choice make a significant difference?

The answer is: It depends on your timeframe. If we look at a comparison of nominal and real household income growth since 1967, the difference between the two deflators is stunning.