Wednesday, February 19, 2014

Accounting for Changes in Inequality

The Berkeley macroeconomics reading group has three themes for this semester: (1) factor shares, wealth, and inequality, (2) misallocation, and (3) financial stability. Each week, a different student presents a paper from one of the topic areas. Today, as part of the first topic, I am presenting the paper "Accounting for Changes in Between-Group Inequality" by Ariel Burstein, Eduardo Morales, and Jonathan Vogel (2013).

Here are my slides. And here is the abstract:
We provide a framework with multiple worker types (e.g. gender, age, education), to decompose changes in aggregated and disaggregated between-group inequality into changes in (i) the supply of each worker type, (ii) the importance of different tasks, (iii) the extent of computerization, and (iv) other labor-specific productivities (a residual to match observed relative wages). The model features three forms of comparative advantage: between worker types and computers, between worker types and tasks, and between computers and tasks. We parameterize the model to match observed changes in worker type allocation and wages in the United States between 1984 and 2003. The combination of changes in the importance of tasks and computerization explain the majority of the rise in the skill premium as well as rising inequality across more disaggregated education types, whereas labor-specific productivity changes drive between-worker wage polarization.
The paper is motivated by the rise in the skill premium, fall in the gender premium, and rise in wage polarization (i.e. relative decline of wages in the middle.) The authors want to know about the role of computerization in these trends. An important idea of the paper is that certain types of workers (e.g. females) may either have a direct comparative advantage at using computers, or might have an indirect comparative advantage in the sense that they have a comparative advantage in occupations in which computers have a comparative advantage. In the first case, we would observe female workers using computers more than males within the same occupation. In the second case, we would observe females being over-represented in the occupations in which all workers use computers a lot.

Using data on computer use and occupations for several years between 1984 and 2003, the authors find that, while women use computers more than men, this is due to indirect comparative advantage. Women are more often in occupations in which all workers use computers more. In contrast, highly educated workers have direct comparative advantage with computers-- they use computers more than less educated workers within the same occupations.

As the price of computers falls, the relative wages of workers with direct comparative advantage in computers rises. So computerization can explain some of the rise in the skill premium (that is, the rise in wages of more educated compared to less educated workers.) A major part of the rise in the skill premium is also attributed to "task shifters," that is, factors like structural changes and international trade that alter the relative demands for workers across occupations.

Computerization does not raise the relative wages of workers with indirect comparative advantage in computers, so computerization does not explain the fall in the gender premium (that is, the fall in male compared to female wages). Both the fall in the gender premium and the relative decline of wages in the middle are attributed to changes in "labor productivity," which in this model is a residual term, meaning it is not actually explained by the model.


  1. I'm about three quarters of the way through "The Second Machine Age", the big new book on the computer/robot/digital revolution by MIT business economist Erick Brynjolfsson and MIT computer scientist Andrew McAfee, and one of the things that surprised me was how much time the authors spend on income inequality and relate it to the digital revolution.

    If you can find the time, very interesting book. I hope to give specifics later, although I could use some time to digest what I've read.


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