One thing to keep in mind is that the reported GDP is net of inflation and the average market return is not. So, 2-3 percentage points of the gap is explained by inflation. We're also sitting at or near all-time highs from a valuation standpoint, so some of that 8-12% is explained by increased valuations. To get 8-12% going forward, we would either need to see a GDP boom or valuations have to keep growing.
That said, valuations do seem to go up at a higher rate than GDP over the long run, even with those issues accounted for. I'm guessing the rest of the issue is some combination of productivity growth and the fact that GDP is defined by national borders and companies are not. There is also likely some impact from credit cycles, particularly the fact that interest rates declined from 1980 to 2022.
Worst book I've quit is Seveneves by Neal Stephenson. What a horrible book!
Worst I've finished is Grapes of Wrath by John Steinbeck, immediately followed by Of Mice and Men by John Steinbeck. I'll throw in a special mention for The Scarlet Letter and The Great Gatsby. All terrible books that I finished only because they were required reading in school.