The figures sound about right. But there are a few complications.
What about people who "disassociated" are they included in the 1% or the 40,000 figures? Probably not. Yet not all of these people left voluntarily, since it can include "apostates", joining military, attending another church, and more recently accepting blood.
Also until the mid 1990s unbaptised publishers could be removed and treated as if disfellowshipped.
Plus we don't know if the DFing rate has changed over the decades, either up or down, which is entirely possible.
Having said that the ball park figure of around 1 million or so DFed seems proportionate and fits with the known facts.