The article discusses different ways to invest for retirement, including simple and more complex strategies. It compares strategies that stay the same over time with those that change based on age. The study shows that some simple strategies work as well as more complicated ones that adjust investments as you get older. Most retirement funds aim to have a mix of stocks and bonds based on your age, with a common target of 120 minus your age for the stock portion. The article suggests that it might be a good idea to have all stocks in your retirement account until about ten years before you retire, then switch to a safer mix of investments.