Louis D. Brandeis, the American jurist, famously warned: “We may have democracy, or we may have wealth concentrated in the hands of a few, but we can’t have both.”

Brandeis’s cri de coeur was inspired by an indignant observation of the shenanigans of America’s robber barons during the Gilded Age. Today, we live in a data-driven age, and some careful students of the connection between money and politics have now amassed a powerful body of evidence to support Brandeis’s moral claim. A lot of it is assembled in a report by the progressive research organization Demos, published this week.

One of the most striking findings is the extent to which economic power translates into political power.

Institutionally, this is an era of unprecedented democracy – one of the triumphs of the 20th century has been the extension of voting rights to all adults in a lot of the world.

But even in the United States, the country that thinks of itself as being the world’s leading democracy, it turns out that those rights do not translate into much actual political power. David Callahan, co-author of “Stacked Deck,” the Demos report, describes the super-rich as “supercitizens, with an outsized footprint in the public square.”