My investing strategy has two stages. The first, more resource intensive, stage is to construct a watchlist of the highest quality shares, by making an assessment of their quality entirely independently of their share prices. The second stage is to select a portfolio from a subset of this watchlist, based on the current prices at the time and what they imply for relative valuations and momentum. I then refresh this selection periodically by rotating shares between the portfolio and watchlist.

My aim is to maintain a watchlist of 100 of the best quality businesses I can find.  This list shouldn’t change much, but I update it every now and again when I come across new candidates. To identify potential candidates I initially use quantitative screens based a small set of quality criteria. I then look at each potential candidate and try to make a judgment of the likely extent, certainty and consistency of future growth in profits relative to the other businesses already on my watchlist. Before making an overall judgment, I first go through a list of smaller questions to break it down:

1. Does the business have ‘good economics’ i.e. consistently high profitability? Does it have little debt? Does it convert profits into cash? Does it have a high return on capital?
2. Does the business have a good track record? Does it have consistent and stable growth in profits and cash over time? Does it have a steadily growing share price over the long term?
3. Does it have a competitive advantage or ‘moat’ that allows it to persistently earn high margins? Is it increasing its market share?
4. What scope is there for more growth? Is it in a growing market? Is it non-cyclical? What is the prospect for geographic expansion?

I have written a post with more detail about identifying quality.

I would be quite happy to buy most of the shares on my watchlist immediately and a viable and sensible strategy for the long term might be to just hold all of them. However, I believe I should be able to do better than this by holding a portfolio of just a subset of those stocks with the best relative valuations and momentum, and by rapidly eliminating any mistakes that might have occurred in my initial shortlisting.

My way of thinking about my portfolio is much more top down rather than bottom up. I don’t think I gain much of an advantage in carrying out very detailed analysis of specific businesses. In fact I think this type of approach can create or exacerbate mental biases: in particular you may unintentionally artificially limit yourself to a very narrow universe of shares that you have looked at in detail, or may become attached to your own research or give undue weight to specific original elements of it.

Detailed research is also a rather time consuming and often ineffective way of managing risk. My approach aims to eliminate a lot of risk by restricting my universe to the very best businesses I can find on the stock market and by following sensible disciplined trading rules that limit the cost of mistakes.

I believe there is a trade off between diversification and conviction. I believe diversification across shares with idiosyncratic risks IS a free lunch in that it can reduce risk without compromising expected returns. I think it is foolish for any investor not to acknowledge uncertainty about the future or the possibility of mistakes. However, it is also true that I have greater conviction in some shares than others and it can be a tricky balance to weigh up how concentrated I should be in a particular position. I will generally start  with a smaller position and then let it grow over time as the price rises and add to it as I get to understand it better and grow more confident in the business.

What shares to buy from the watchlist? I will consider overall portfolio diversification when choosing what to buy but mostly I will be guided by:

1. Whether a share has strong momentum – in particular from recent good news (as this momentum tends to suggest the price has underreacted). Otherwise shares with steadily increasing prices or breakouts to new highs tend to look attractive to me. I also sometimes like bounces off ‘support’ where there is still a long term upward trend.
2. Where valuation is cheaper – I will typically consider the relative valuations of potential candidates using a simple DCF approximation (like the Graham rule of thumb). Given the inherent uncertainty in this sort of exercise, I use it more as a method to filter out candidates where the valuation looks too demanding, rather than as the deciding factor between shares where either valuation seems reasonable.

When to trade? I think the key is unequivocally to run winners and sell losers as ruthlessly as possible. I’ve found the challenge is to calibrate this correctly to avoid overtrading. After a period of using stop losses, I’ve found a better system for me is one of periodic rotation, where I replace the weakest momentum position from my portfolio with one from my watchlist no more than once every two weeks. I also always sell immediately on a profit warning. The research I’ve seen on this suggests that selling on the day of a profit warning is the best thing to do the vast majority of the time.

You will have noticed that my investing strategy, while allowing some judgment, has clearly defined rules. This is because I believe trading discipline is very important – our natural instincts are more often than not to do exactly the wrong thing. Sometimes this is to stare like a rabbit in the headlights at a plummeting share price when you have made a mistake but are unwilling to admit it. Sometimes this is to avoid buying something because the price is annoyingly higher than when you first spotted it or because you recently sold it. Using momentum based rules allows me to avoid behavioural biases and instead exploit those of other investors.