The overall purchasing power of the dollar generally tends to go down over time just like any other country’s currency. This phenomenon is summarized by the term inflation. Because governments continue to print money, there continues to be more and more money in the system. The more money there is in the system, the less each unit of that money is worth, so long as the value of everything going on in the system remains the same. This is because there are more units of money (dollars) but the value of the pie (economy) remains the same. In reality, the economy does not remain the same, but the increase in dollars happens at a faster rate than the increase in the actual economy. The ongoing pandemic and The Federal Reserve's response to it have provided an extreme example as the economy has contracted while the money supply has increased, both at unprecedented rates. Some of this is fairly complex and theoretical macroeconomics but the proof is in the past. The cost of a banana is probably not going back to a nickel.