The fatality rate is the number of cases that result in death divided by the total number of cases (for each gender-age group) excluding cases within the past 45 days (or at the time of writing this, May 25). The basic idea is to only include cases that are not time-censored; that is, they have had enough time to develop until recovery or death.
Despite the repeated assertions by certain politicians that Florida has the best data (still waiting on hospitalizations, Ron), it is actually lacking in many areas that hinder a more complete understanding of the situation. For example, case data is overwritten each day with no record of the days between when Died field goes from ‘No’ to ‘Yes’ (time until death). We cannot even be entirely sure that cases are the same from day to day as there is no unique id and the count of cases by case date changes each day (always lower for some reason).
The only way to estimate time from case until reported death is to look at the change in the number of deaths from one day’s case file to the next. Unless you have been saving each day’s file (we have, as have many others), it would be impossible to know how many new deaths were reported and get an estimate for when a certain proportion of deaths have come in. This is where the 45 day lag comes in.
Now that I’ve wasted all your time, I’ll get to the point. We just look at the percentage of deaths (by case date) for each consecutive case file. Using case dates that are at least 60 days old, we looked at how many of the total/almost total deaths that have been reported by day 45, which is about 96% of them.