Last Friday, the Center for American Progress, the center-left think tank founded by Bill Clinton’s former chief of staff John Podesta, held a conference to launch its new Washington Center for Equitable Growth. The new center, which is being funded by the Sandler Foundation, will finance academic research into the causes and effects of inequality, broadly conceived, and function as a hub for policy makers, journalists, and others involved in the subject.

It was an interesting morning, featuring some of the top researchers in the field, and I moderated one of the panel sessions. In some brief opening remarks, I noted that Washington has long had a number of centers promoting inequitable growth, so it only seems fair to have one supporting equitable growth. And having learned a good deal from the panelists, I thought it might be worthwhile to share some of the charts they brought with them. Taken together, the pictures convey a good deal of what we know about inequality. They also raise important questions about the channels through which it impacts economic growth and human development.

I’ll start with an updated chart from Emmanuel Saez, of Berkeley, which shows the share of pre-tax income enjoyed by the top one per cent of earners over the period from 1913 to 2012. The data, which comes from the Internal Revenue Service, is for market income: it includes realized capital gains but excludes government transfers.

The U shape of the chart should by now be familiar. After rising in the Roaring Twenties, the income share of the one per cent fell sharply in the postwar period. Since the late nineteen-seventies, it has been climbing again, albeit in a somewhat zig-zag fashion. The top earners’ share of overall pre-tax income peaked at about twenty-four per cent in 2007, fell back during the Great Recession, and then recovered strongly. In 2012, it was about twenty-three per cent.

How have the folks outside the one per cent been faring? A second chart from Saez tells us the answer. Going back a century, the light line shows the path of inflation-adjusted pre-tax incomes for families in the bottom ninety-nine per cent. The dark line shows how families in the top one per cent have been doing.

Once again, the long-term trends are clear. Between the start of the Second World War and the first oil-price shock of 1973, families in the bottom ninety-nine per cent saw their incomes rise sharply. With the exception of the late nineteen-nineties, the past forty years have been marked by slow growth. For those at the top of the income distribution, recent history has been very different. After growing modestly in the postwar decades, the incomes of families in the top one per cent took off in the late nineteen-seventies, and have been zig-zagging upward since then.

The United States is a very unequal country. But how much does it differ from other industrialized countries? And what difference do taxes and government transfers make? (If the tax and benefits system is ameliorating inequality that the market generates, it might change the way we think about the issue.) Presenting data from the invaluable Luxembourg Income Study, of which she is a director, Janet Gornick, a political scientist at the CUNY Graduate Center, provided answers to both of these questions.

The third chart shows a measure of pre-tax inequality and inequality after taxes and transfers for twenty-two advanced countries. The measure used is a Gini coefficient, which captures inequality on a scale of zero to one, where zero is perfect equality (everybody receives the same income) and one is perfect inequality (the richest person gets all the income). The light lines on the bar chart show pre-tax inequality. The dark lines show inequality after taxes and transfers.