taken by various groups.

May be kinda confusing. They do not include the bottom.

90-95th is part of the top 10%. The lower part of it, but still higher than 90%. So the top 10% is broken in to
top 1%
top 4% (meaning top 5% without top 1%)
next 5% (top 10% without the top 5%, or 90-95th percentile)

My point being that, while the gains of the top 1% are very large, the other parts of the top 10% have been taking bigger slices of the pie too - leaving that much less for the bottom, and the middle.

If the top 10% gets 48%, the bottom 50% gets 12%, then the middle 40% gets 40%.

Back in 1986 it was top 10% got 35%, bottom 50% got 17%, middle 40% got 48%. http://www.koch2congress.com/5.html

Unfortunately, I cannot find those stats going back before 1986.