There are a couple of finance theories that have shaped the investment strategies of fund managers for the last couple of decades.
The Capital Asset Pricing Model (CAPM) is one of those:
http://en.wikipedia....t_pricing_model
CAPM theory suggests that assets can be diversified in a portfolio, and that different portfolios will have different return/risk ratios. Risk is measured in return variance. The set of portfolios with the highest return/risk ratios will create the efficient frontier:

When considering a risk free rate of return, it is theoretically not possible to get a higher return/risk ratio of a portfolio of assets than a linear combination of weightings in the risk free asset and the Tangency Portfolio (or market portfolio). By borrowing at the risk free rate you can leverage your investments along the line beyond the Tangency Portfolio. The risk free rate has always been considered to be government bonds!
The second theory (or hypothesis): the Efficient Market Hypothesis (EMH) - says that you cannot beat the market. Well, you can try, but it is nearly impossible. The market adjusts so quickly to any new information that the only rational choice is to just buy the index and try to keep up with the market performance. This is probably why so many super funds perform close to the overall ASX index.
Now, here are my questions:
1) What happens when the government bonds yields go above the so called Market Portfolio? In theory, nobody would hold any asset other than the government bonds. This is clearly false.
2) What happens when the government bond yields go to zero? In theory, this should make investors leverage up like crazy. That doesn't seem to be the case either.
Are CAPM and EMH theories just bovine scatological substance?
This post has been edited by AndersB: 25 November 2011 - 01:54 AM

Help




















