year,top10_sp500_pct,source
1900,24.0,Finaeon
1929,16.0,Finaeon
1950,18.0,Finaeon estimate
1964,19.0,Counterpoint Global
1970,16.0,Counterpoint Global
1980,15.0,Counterpoint Global
1990,16.0,Counterpoint Global
1999,25.0,Counterpoint Global dot-com peak
2013,17.0,Counterpoint Global trough
2020,28.0,Counterpoint Global
2023,30.0,Counterpoint Global
2025,35.0,Visual Capitalist / FactSet