Mint Explainer | New Covid death estimate: Does the Indian government’s rebuttal hold water?

The study was conducted in Scientific advances A journal published on July 19 said life expectancy at birth was 2.6 years lower and mortality 17% higher in 2020 compared with 2019. This is for a subsample of 14 states and union territories, but the authors said that if other states followed the same trends, it would mean 1.19 million additional deaths across India in 2020. The study found that life expectancy fell more among women than men, and also more among children and among marginalized groups. Mortality was particularly high in the last four months of 2020.

mint explains how to read the numbers and understand the nuances of official death estimates in a country where many deaths go unreported.

First, what is excess mortality?

Of course, governments fail to capture the true death toll of a pandemic like Covid-19: not all patients are tested and the definition of a “Covid death” is complicated. Therefore, the “excess mortality” approach is the best way to estimate the number of victims.

The “excess mortality” approach is the difference between the number of deaths in an unusual period (such as 2020 and 2021) and the number of deaths in a normal year. This can give a sense of the direct and indirect consequences of a pandemic such as Covid-19.

How did the new study arrive at its estimates?

The latest estimate is eight times the official number of Covid-19 deaths in India in 2020 and 1.5 times the World Health Organization’s estimate of excess deaths. It is based on the latest National Family Health Survey (NFHS), for which fieldwork was conducted between June 2019 and April 2021. The survey includes questions designed to assess a family’s life expectancy and recent death history.

The study used data from a subsample of households surveyed by the NFHS, interviewed during the four months of 2021, representing 23.2% of the total sample and spanning 14 states. To explain the credibility of this method, the study first notes that the mortality estimates thus derived by the NFHS for 2018 and 2019 (based on households’ recall of recent deaths) are consistent with estimates from other official data, such as the Sample Registration System (SRS, which uses a nationally representative sample of households each year to estimate death rates, among other things). However, this was not the case for 2020.

How is the government reacting to this?

The Indian government, in its rebuttal, said the data from 14 states could not be extrapolated to the entire country. It also said there could be reporting and selection bias in the selected subsample as the data was collected at the peak of the pandemic. The Centre said the study failed to take into account that the SRS data for 2020 showed no increase in death rates and no reduction in life expectancy.

The report’s finding that more women and children died contradicts official data, but the study did not comment on the claim that the mortality rate was higher among marginalized groups.

Tell me more about how else one can estimate excess mortality.

In India, the Civil Registration System (CRS) counts the number of deaths registered in a given year. However, this is not enough as it does not include the unregistered deaths. For this purpose, in previous years, the CRS reported both the registered deaths and the estimated total number of deaths (the latter relied on the SRS). It shows that 92% of deaths in India were registered in 2019, up from 85% in 2018.

The CRS report for 2020 (the latest year for which it is available; published in early May 2022, a day before the WHO estimates were scheduled to be released) only reported the number of registered deaths (8.1 million, a 6.2% increase) that year. One cannot estimate the number of excess mortality without also having a figure for estimated deaths, which tends to be much higher. This estimate was, oddly enough, published a few days later by the Press Information Office and contradicted the WHO estimates.

It claimed that 99.9% of deaths in 2020 were registered, and therefore the 8.1 million figure was a reasonably accurate measure of the true number of deaths that year. This effectively meant that the official estimate of deaths (and not just registered deaths) in India in 2020 was actually lower, at 8.1 million, down from 8.3 million in 2019.

Why do researchers try to calculate excess mortality using indirect methods?

First, because the 99.9% registration figure for 2020 is too good to be true (especially for a country like India in a year hit by lockdowns). Second, because crucially, the CRS for 2021, the year when Covid peaked, is still awaited. Such a delay is unusual and makes an official estimate of “excess mortality” difficult.

This is where studies like the new one come in, which try to derive indirect estimates from other sources, as they fill the gap left by official data. The WHO estimates were based on incomplete official estimates from 17 states and union territories.

Did the study take into account the points raised by the Centre?

Yes, in many ways. The study acknowledges that analyzing 14 states may not be enough to understand national trends, but it says that the changes in mortality trends in the subsample may not have been all that different from the rest of India. This claim is based on a national serosurvey that had shown that the spread of the virus was similar in the subsample states.

The study also says that its estimates were accurate even in hypothetical subsamples within the subsample, lending credibility to the extrapolation. However, to account for any errors in the extrapolation method, the study gives a wider range of estimates, with 1.19 million as the midpoint. The study is 95% confident that the figure for all of India was between 730,000 and 1.65 million.

The study also says that the CRS data in states with high mortality rates showed patterns of excess mortality that were broadly consistent with the NFHS data.