Some good discussion here. I always ask "give me your assumptions" to those who claim that past performance of the S&P index indicates it ought to outperform BRK going forward. They never provide them. Trends are nice, but some trends, such a falling interest rates, falling taxes, and multiple expansion can't go on forever.

WEB asked this question in 1999,

"The INESCAPABLE FACT is that the value of an
asset, whatever its character, cannot over the long term grow faster
than its earnings do.
Now, maybe you'd like to argue a different case. Fair enough. But give
me your assumptions. If you think the American public is going to make
12% a year in stocks, I think you have to say, for example, "Well, that's
because I expect GDP to grow at 10% a year, dividends to add two
percentage points to returns, and interest rates to stay at a constant
level." Or you've got to rearrange these key variables in some other
manner. The Tinker Bell approach'clap if you believe'just won't cut it."