In his new book The Great Experiment, political scientist Yascha Mounk digs into how tough it is for very diverse democracies to treat all their citizens equally. The price to pay if it goes wrong is high: society falls apart.

The US faces many ongoing challenges, especially on race relations, but has done much better in some areas than was predicted decades ago – for example, the increasing frequency of interracial marriages, Mounk tells Ian Bremmer.