From the interview:
CHANG: Wow. There's such a disparity there. How did researchers arrive at this new estimate? Like, how can they be certain all of those deaths were from COVID?
PATHAK: So they used a few different methods. First, they looked at civil death registers. So these would be death certificates. But again, this information was only available from some state governments in India. The second thing they looked at was infection rates. India has conducted these big national surveys to check for coronavirus antibodies in the population, which gives you a sense of how many people were infected. The researchers used fatality rates from other countries to extrapolate what percentage of Indians who have got the virus may have died. Finally, the third source of data was an economic survey by an Indian think tank, which mostly has information about topics like unemployment but also about mortality.
