There are a number of concepts in investing that are treated as though they are as well
thought out as gravity—simple, inexorable, and undeniable. The basic idea of
rebalancing as it is typically put to investors seems reasonable. Over time, certain parts
of a portfolio will out-perform and certain parts will under-perform. At the end of some
period of time, those assets that have done really well will make up a higher fraction of
your portfolio and vice versa. If you are shooting for a portfolio with a specific
allocation to sectors or individual positions, you will then sell some fraction of the betterperforming
assets and buy more of the under-performing assets to bring the percentages
back to the original target...Mr. Bogle’s analysis [however] suggested that annual re-balancing adds no net value. He looked at
a portfolio with a target allocation 50% S&P500 / 50% bonds for all 25-year periods from
1826 to the present. He also looked at a portfolio with a target allocation that is 48%
S&P500, 16% small cap, 16% international, and 20% bonds over the past 20 years. In
both cases, he found no value added by annual re-balancing. Consider, however, the
powerful intuitive case in favor of rebalancing—albeit anecdotally. If you were riding
the dot-com wave and had annually re-allocated by selling some of your high fliers and
buying under-performing assets that exhibited low correlation to tech stocks (like utilities
or REIT’s), you would certainly be better off today than if you did not rebalance. How
do we reconcile the commonsense perspective from the dot-com era with Mr. Bogle’s
results?
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