Two charts in a 2013 American Economic Review (AER) article put numbers to the “hollowing out” of middle class America – a topic celebrated with profuse anecdotes in the media.

The top figure shows the change in employment 1980-2005 by skill level, based on Census IPUMS and American Community Survey (ACS) data. Occupations are ranked by skill level, approximated by wages in each occupation in 1980.

The lower figure documents the changes in wages of these skill levels 1980-2005.

These charts are from David Autor and David Dorn – The Growth of Low-Skill Service Jobs and the Polarization of the US Labor Market – who write that,

Consistent with the conventional view of skill-biased technological change, employment growth is differentially rapid in occupations in the upper two skill quartiles. More surprising in light of the canonical model are the employment shifts seen below the median skill level. While occupations in the second skill quartile fell as a share of employment, those in the lowest skill quartile expanded sharply. In net, employment changes in the United States during this period were strongly U-shaped in skill level, with relative employment declines in the middle of the distribution and relative gains at the tails. Notably, this pattern of employment polarization is not unique to the United States. Although not recognized until recently, a similar “polarization” of employment by skill level has been underway in numerous industrialized economies in the last 20 to 30 years.

So, employment and wage growth has been fastest in the past three or so decades (extrapolating to the present) in low skill and high skill occupations.

Among lower skill occupations, such as food service workers, security guards, janitors and gardeners, cleaners, home health aides, child care workers, hairdressers and beauticians, and recreational workers, employment grew 30 percent 1980-2005.

Among the highest paid occupations – classified as managers, professionals, technicians, and workers in finance, and public safety – the share of employment also grew by about 30 percent, but so did wages – which increased at about double the pace of the lower skill occupations over this period.

Professor Autor is in the MIT economics department, and seems to be the nexus of a lot of interesting research casting light on changes in US labor markets.

In addition to “doing Big Data” as the above charts suggest, David Autor is closely associated with a new, common sense model of production activities, based on tasks and skills.

This model of the production process, enables Autor and his coresearchers to conclude that,

…recent technological developments have enabled information and communication technologies to either directly perform or permit the offshoring of a subset of the core job tasks previously performed by middle skill workers, thus causing a substantial change in the returns to certain types of skills and a measurable shift in the assignment of skills to tasks.

So it’s either a computer (robot) or a Chinaman who gets the middle-class bloke’s job these days.

And to drive that point home – (and, please, I consider the achievements of the PRC in lifting hundreds of millions out of extreme poverty to be of truly historic dimension) Autor with David Dorn and Gordon Hansen publihsed another 2013 article in the AER titled The China Syndrome: Local Labor Market Effects of Import Competition in the United States.

This study analyzes local labor markets and trade shocks to these markets, according to initial patterns of industry specialization.

The findings are truly staggering – or at least have been equivocated or obfuscated for years by special pleaders and lobbyists.

Dorn et al write,

The value of annual US goods imports from China increased by a staggering 1,156 percent from 1991 to 2007, whereas US exports to China grew by much less…. 

Our analysis finds that exposure to Chinese import competition affects local labor markets not just through manufacturing employment, which unsurprisingly is adversely affected, but also along numerous other margins. Import shocks trigger a decline in wages that is primarily observed outside of the manufacturing sector. Reductions in both employment and wage levels lead to a steep drop in the average earnings of households. These changes contribute to rising transfer payments through multiple federal and state programs, revealing an important margin of adjustment to trade that the literature has largely overlooked,

This research – conducted in terms of ordinary least squares (OLS), two stage least squares (2SLS) as well as “instrumental” regressions – is definitely not something a former trade unionist is going to ponder in the easy chair after work at the convenience store. So it’s kind of safe in terms of arousing the ire of the masses.

But I digress.

For my purposes here, Autor and his co-researchers put pieces of the puzzle in place so we can see the picture.

The US occupational environment has changed profoundly since the 1980’s. Middle class jobs have simply vanished over large parts of the landscape. More specifically, good-paying production jobs, along with a lot of other more highly paid, but routinized work, has been the target of outsourcing, often to China it seems it can be demonstrated. Higher paid work by professionals in business and finance benefits from complementarities with the advances in data processing and information technology (IT) generally. In addition, there are a small number of highly paid production workers whose job skills have been updated to run more automated assembly operations which seem to be the chief beneficiaries of new investment in production in the US these days.

There you have it.

Market away, and include these facts in any forecasts you develop for the US market.

Of course, there are issues of dynamics.