Motorcyclists wait at a checkpoint in Jakarta, Indonesia, on Wednesday, Aug. 4, 2021. Southeast Asias largest economy has been topping the worlds tally of daily Covid-19 deaths as the delta variant spreads through the country and overwhelms its hospitals. Photographer: Dimas Ardian/Bloomberg 
The other biggest contributors are also in Asia. They include countries like Indonesia -- projected to have the world’s fourth-biggest middle class by 2030, overtaking Russia and Japan -- and Bangladesh, a densely populated country the size of Iowa, which is set to rise up the rankings faster than any other nation. It’s forecast to jump from 28th to 11th place, adding more than 50 million middle-class consumers.
Asian countries already make up more than half of the world’s middle class, but they account for only 41% of that group’s consumer spending, according to the study. The share is set to exceed 50% by 2032.
China, India and the U.S. are projected to retain the top three rankings as the countries with the largest middle-class populations, according to World Data Lab. Slow or negative population growth in some advanced economies will lead to a shrinking middle class in countries like Japan, Germany, Italy and Poland.