It's such a bad assumption that historical returns on capital will persist. Capital is subject to supply/demand just like other things. The more of it there is,

It's such a bad assumption that historical returns on capital will persist. Capital is subject to supply/demand just like other things. The more of it there is, the lower the returns are. Anyone who works in finance/investing will tell you (including old Warren Buffett), it's a lot harder to generate returns these days than 50 years ago. There is just so much capital sloshing around.