My earlier answer touched on sources for making bubble charts, but I need to add more on how to get the data for those charts. A possible start might be the Census Bureau, which gets 4 hits for: inequality debt "time series" (use the tiny search box at upper right); and 15 hits for: inequality 1970s. You might do well to skim quickly through the list of about 150 for: inequality "time series", in case they might have many different words implying inequality.

You can also try, which gets "about 322" hits for: Inequality debt "time series" 1970 2012. But note that this Bing search engine does a smart extract of what it finds most relevant - if you wait a minute or 2, that list drops to 35 or 36 hits. Compare a Google search for: Inequality debt "time series" 1970 2012 site:gov , which gets 168 hits. Note that Google's site:gov limiter will get different results than - partly because that site includes STATE as well as federal sites and documents, including ones with the old URLs like,,, etc. In Google you can also limit to site:edu , which will get some free research reports, preprints, etc. - very different from the results in, which is mostly commercial subscription journal articles, that .require you to be on campus at a subscribing university, or at least logging in via a student/staff password to their proxy server.

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