I don’t know what they mean by income data, but let’s use the GDP as a proxy.
2025 GDP (Current USD) - $3.5Tn (actually 2023, but it’s probably still close) Population - 1.45Bn Bottom Half Population - 725mm Bottom Half share - 15% Bottom half share of GDP - $525Bn Bottom half GDP per capita - $725
1990 GDP (current USD) - $320Bn Population - 870mm Bottom Half population - 435mm Bottom Half Share - 22.2% Bottom Half Share of GDP - $71Bn Bottom Half GDP per capita - $163
So the bottom half per capita GDP in current USD has risen from $163 to $725, almost a 4.5x increase.
The increase in inequality is not good, but this isn’t the economic catastrophe for India’s poor that this article is presenting it as. In fact, a 4.5x increase in per capita income in 35 years is a significant achievement for a country of Indias size and diversity. It of course pales in comparison to what China has achieved, but what doesn’t pale in comparison to what China has achieved.