Joe sold stock for $1,000 that he bought a year ago for $1,000. He says, “At least I didn’t lose any money on my financial investment.” However, his economist friend points out that, in effect, he did lose money because he could have received a 2% return on the $1,000 if he had deposited the money in a savings account instead of buying the stock.
In this case, the economist’s analysis incorporates the idea of ___.