Warren Buffett: Quantitative vs Qualitative Investing

In Buffett Partnership Letter October 9, 1967, Buffett said,

“The evaluation of securities and businesses for investment purposes has always involved a mixture of qualitative and quantitative factors. At the one extreme, the analyst exclusively oriented to qualitative factors would say, “Buy the right company (with the right prospects, inherent industry conditions, management, etc..) and the price will take care of itself.” On the other hand, the quantitative spokesman would say, “Buy at the right price and the company (and stock) will take care of itself.” As is so often the pleasant result in the securities world, money can be made with either approach. And, of course, any analyst combines the two to some extent – his classification in either school would depend on the relative weight he assigns to the various factors and not to his consideration of one group of factors to the exclusion of the other group.

Interestingly enough, although I consider myself to be primarily in the quantitative school (and as I write this no one has come back from recess – I may be the only one left in the class), the really sensational ideas I have had over the years have been heavily weighted toward the qualitative side where I have had a “high-probability insight”. This is what causes the cash register to really sing. However, it is an infrequent occurrence, as insights usually are, and, of course, no insight is required on the quantitative side – the figures should hit you over the head with a baseball bat. So the really big money tends to be made by investors who are right on qualitative decisions but, at least in my opinion, the more sure money tends to be made on the obvious quantitative decisions.

Such statistical bargains have tended to disappear over the years. This may be due to the constant combing and re-combing of investments that has occurred during the past twenty years, without an economic convulsion such as that of the ‘30s to create a negative bias toward equities and spawn hundreds of new bargain securities. It may be due to the new growing social acceptance, and therefore usage (or maybe it’s vice versa – I’ll let the behaviorists figure it out) of takeover bids which have a natural tendency to focus on bargain issues. It may be due to the exploding ranks of security analysts bringing forth an intensified scrutiny of issues far beyond what existed some years ago. Whatever the cause, the result has been the virtual disappearance of the bargain issue as determined quantitatively – and thereby of our bread and butter. There still may be a few from time to time. There will also be the occasional security where I am really competent to make an important qualitative judgment. This will offer our best chance for large profits. Such instances will, however, be rare. Much of our good performance during the past three years has been due to a single idea of this sort.”