After last week's post on the relative benefits of renting versus buying a home, Ryan Decker sent me to his earlier post on the subject. In it Ryan mentions an interesting concept I'd never heard of before; lifecycle investing . Developed by Ian Aryes and Barry Nalebuff ( pdf ), the idea is that investors in their twenties can reduce risk and improve returns not only by investing all their savings in the stock market, but by going one step further and taking out a loan to buy stock. Odd advice, right? But there are good reasons for this. Aryes and Nalebuff's thesis begins with the idea that we all own something called a "human capital bond." This is the present value of our lifetime stream of saved wages. Imagine a young investor with an average tolerance for risk who has just entered the labour force. He/she possesses a human capital bond that is currently worth, say, $500,000. Let's assume that this bond is expected to be quite stable in value, maybe be...