The Problem with Back Testing Investing Strategies for Practical Investors
In surveying some of my favorite blogs recently, I have come upon something that hadn’t previously occurred to me, but could potentially alter how I invest. That is the problem with back testing Investing Strategies. Greenbackd posted an interesting starter piece on this subject called Walking the Walk, that led me back to the original blog from Aswath Damodaran called Transaction Costs and beating the Market. I have often thought there were practical problems with back testing, but I had not tried to articulate them until I read these posts. Both are excellent and worth reading. Damodaran, who is a Finance professor at NYU, and an author of Investment Fables (which I own), writes about the many ways to beat the market in general terms and then goes on to say, “Most of these beat-the-market approaches, and especially the well researched ones, are backed up by evidence from back testing, where the approach is tried on historical data and found to deliver “excess returns”.
What is Focus Investing?
The concept of Focus Investing is devilishly simple. Take the magnifying glass out and focus it on the very best investment ideas you have. Don’t pull the investment trigger unless you can say this is too good to pass up. It is the extreme opposite idea of diversifying your investments in the manner suggested by many financial advisors.