So, for example, if the peak utility of money (the time when it can bring optimal usefulness or enjoyment) occurs at age 30, then at age 30 every dollar buys you one dollar’s worth of enjoyment. By age 50, the utility of money has declined considerably: Either you would get a lot less enjoyment out of that same dollar or you would need more money (say, $1.50) to obtain the same amount of enjoyment as you got out of $1 back when you were a healthy, vibrant 30-year-old.
