Even the death figures reported in 2020 and 2021 are not final. The more than 21,000 deaths reported by Kerala in the past four months have not all occurred this year. Most of them relate to the last year. The 1,300 deaths Assam added on April 25 did not all occur that day, month or year. They probably happened the year before. Several hundred or even thousands of deaths that states have adjusted in 2021 would have actually occurred in 2020. Additions to the overall count are made on the day these deaths are confirmed, not the day they could have occurred.
It is difficult to gauge the magnitude of the undercount in a situation like this, especially when the counting exercise is still ongoing. A physical count and verification of the dead in a country as vast as India during such a chaotic time is bound to take a little longer than running some equations in a computer model.
The WHO report does not enter into the calculation of the magnitude of the undercount, for India or any other country. He did a more direct exercise in calculating excess mortality. He estimated the total number of people who probably died in India in 2020 from all causes and, from this, subtracted the expected number of deaths from all causes if there were no Covid. These “excess” deaths are considered a direct or indirect consequence of Covid-19.