To understand the example, think of it as a portfolio consisting of cash and one stock (AMZN). The "amount invested" column is the total amount that has been invested in the portfolio.
So, to get the return, we are dividing total value (stock value + cash) by the amount invested.
In 2005 and 2007, we could make the buys using only the cash pool. We didn't have to invest more money into the portfolio. So, the "amount invested" column didn't change, but the "cash pool" column decreased.
Register for free to join our community of investors and share your ideas. You will also get access to streaming quotes, interactive charts, trades, portfolio, live options flow and more tools.