It is well-known that expected portfolio growth is maximized by maximizing
expected logarithmic utility. This investment criterion is known as Kelly betting.
It has many optimality properties but is considered to be risky. Blackjack
teams and other advantage gamblers practice a fraction of the Kelly optimal to
decrease risk. Some hedge fund managers are thought to practice according to
Kelly principles. We use a continuous multivariate Geometric Brownian motion
model and present an interval estimate for the historical fraction for a portfolio
of correlated bets, possibly including a risk-free asset. Historical data comes
from a range of sources and the results provide a risk aversion statistic, which
corresponds to an isoelastic utility function and level of relative risk aversion
