Defining the proportion in which different types of assets are allocated in a portfolio is a crucial part of an investment plan, and a key risk management measure. The three main areas whose proportions are normally considered when defining an asset allocation are stocks, bonds, and cash. On the stock/bond ratio, an example of an asset allocation recommended by John Bogle (2017), founder and chief executive of the Vanguard Group, is that younger investors could allocate 80 percent to stocks, preferably in the form of low-cost index funds, and 20 percent to bonds, with these proportions changing to 70 percent in stocks and 30 percent in bonds for older investors, while also considering that the proportion of bonds could go as high as 40 or 50 percent for people in the post-retirement phase. According to E*Trade (2022), a conservative asset allocation is 20 percent stocks, 70–75 percent bonds, and 5–10 percent cash; a moderate asset allocation is 60 percent stocks, 30–35 percent bonds, and 5–10 percent cash; and an aggressive asset allocation is 80–90 percent stocks, 0–15 percent bonds, and 0–5 percent cash. Many financial websites have asset allocation calculators that can help investors define with greater precision what their recommended asset allocation would be. However, a rule of thumb that many financial specialists use to quickly assess the proportion of stocks in relation to bonds is the rule of 110, which involves subtracting the age of the person from 110, with the result indicating the percentage in equities. For instance, a person who is twenty-five years old could have a portfolio that consists of 85 percent stocks and 15 percent bonds, while a person who is fifty years old could have a portfolio with 60 percent stocks and 40 percent bonds. This rule, however, would need to be taken into consideration together with other factors such as risk tolerance, time horizon, source of income, investing experience, and financial goals, among others.