>So high profits and high inflation suggests an economy dominated by monopolies,
then pivot to
>Competition has decreased throughout the economy.
Competition decreasing is a far cry proving "an economy dominated by monopolies," which is simply not true.
>Or, to take another measure, in 1999 there were 8,000 companies listed on USA stock markets, but now there are only 3,400 companies
That says more about stock markets than number of companies. Fortunately the Census Bureau tracks relevant facts (and there are more at the BLS), and their data puts literally millions more businesses in 2019 [1] (the last year they have data) than in 1999 [2].
And nothing in their data supports "suggests an economy dominated by monopolies".
Care to explain how you measure dominated? As is most of consumer money is spent there? As in the majority of businesses? As in what?
[1] https://www.census.gov/data/datasets/2019/econ/susb/2019-sus...
[2] https://www.census.gov/data/datasets/1999/econ/susb/1999-sus...