The World Bank isn’t relying on either of these standard measures. The bank is instead pushing a statistical notion of “shared prosperity” that, as Ghosh puts it, “leaves the rich out of the equation!” This World Bank measure defines success in the battle against inequality as what we have when the incomes of the bottom 40 percent are growing faster than the national average income.

On the World Bank’s scorecard, in other words, any nation where the incomes of the top 1 percent are rising ten times faster than the national average income would be making “progress” against inequality so long as the incomes of the bottom 40 percent were rising slightly faster than that national average.

This “bizarre notion of ‘shared prosperity,’” says Jayati Ghosh, “provides very misleading estimates of the extent of inequality or progress in reducing it.”

By this bizarre World Bank yardstick, over half the world — 53 percent of the nations the bank sampled — were making progress against inequality just before the pandemic hit and another 11 percent were showing no change.

Researchers with the World Inequality Database, an ambitious statistical effort that takes inspiration from the ground-breaking research of scholars like Thomas Piketty, paint a starkly different picture. Only 26 percent of the world’s nations, as measured by the Gini coefficient, are actually showing progress against income inequality, and only 12 percent are showing progress in Palma-ratio terms.

For three top global inequality watchdogs — Oxfam, the Development Finance International, and the New York University Center for International Cooperation’s Pathfinders initiative — the World Bank’s “shared prosperity” scorekeeping makes plain the need for a real “data revolution” that spotlights the wealth of the world’s wealthiest.

The World Bank’s current approach, these three groups charged in a new report released last month, essentially “ignores what is happening to the rich.” We cannot afford that ignoring, the groups stress, not at a time when “the world’s wealthiest citizens continue to be largely responsible for extreme carbon emissions” while the world’s “poorest citizens pay the price through climate disasters.”

Will critiques like this get the World Bank to change its statistical ways? We’ll see. The bank’s first reaction to the economists’ open letter has been somewhat encouraging. The World Bank, says a spokesperson, agrees “we need to do more to address inequality” and “do better in measuring progress.”