Why India’s total economic output today is where China’s was in 2007

Roughly speaking, China started modernising its economy a decade before India did in the late 1970s. Not only did China start earlier, it also grew at a brisker pace. Compounding, as students of mathematics know, does the rest — India’s total economic output today is where China’s was in 2007, so India is about 16 years behind, even if, going forward, it grows at the same pace that China grew at.
Of course, such high growth rates may now be elusive, and catching up will require yet more time even if all goes well for India, since China will not remain stagnant.