In any case, this page is about position sizing and not portfolio theory. I don't know what this does to the profitability of the method because the article's author didn't discuss this. In the percent volatility example, the computation would be: ($10,000 x 2%) / 1.25 or 160 shares. Use the same formula to determine the share size. One way to avoid the concentrated portfolio problem is to divide the $100,000 into $10,000 allotments (or whatever size you feel comfortable with that would lead to a diversified portfolio), one for each stock. (Of course this assumes that the stocks share the same buy price, volatility, and so on). The percent-risk method would be even worse with $40,000 used for just one stock. Thus, you can buy just over 3 stocks, giving you a concentrated portfolio. The downfall of these two methods is that if your portfolio is $100,000, then the trade just described would chew up 1,600 shares x $20 buy price or $32,000. Instead of calculating the 10-day exponential moving average of the true range, I just calculate the volatility using, which provides it at the click of a button. For example, if the current account equity (CE) is $100,000, the percent of portfolio equity we want to risk (%PE) is 2%, and the stock's volatility is $1.25, then the result is: ($100,000 * 2%) / $1.25 or 1,600 shares. SV is the stock's volatility (10-day EMA of the true range). PositionSize = (CE *%PE) / SV Where CE is the current account equity (size of portfolio). Tests described in the article say it performs much better than the percent risk method. Percent Volatility Position Sizing The percent volatility position sizing method adjusts the risk according to the stock's volatility. The formula for this approach is: DollarRiskSize/(BuyPrice - StopPrice) In this example, the DollarRiskSize is $2,000, the BuyPrice is $20 and the StopPrice is 19 giving a result of $2,000/($20 - $19) or 2,000 shares. For example, if you are looking to buy a stock with a price of $20 and a stop loss of $19, with a maximum loss of $2,000, you should buy 2,000 shares. Percent Risk Position Sizing The first method, percent risk position sizing, is well known and it's based on risk to determine the position size. I already use volatility to determine stop placement (see ), so this was a welcome addition.
In the August 2007 issue of Active Trader magazine (), Volker Knapp (see Trading system lab: 'Percent volatility money management') tested a system that used volatility to determine the position size. As I learned about the stock market, I knew that there were better ways to position sizing (money management) but I didn't know what they were. I thought that's the method that everyone used. That bought me 100 shares of a $20 stock. Position Sizing Spreadsheet Excel in introduction. Experiment with different position sizing techniques.
Position Sizing Background For most of my investing career, I used a fixed dollar amount for money management when buying stocks.