If you asked a sample of Americans "What is the temperature of Mars?" about 8% would say they don't know.
If something cannot go on for ever, it will stop
Consumer: A person who is capable of choosing a president but incapable of choosing a bicycle without help from a government agency.
Psychiatrist to patient: Maybe you don't have a complex. Maybe you are inferior.
If something is inevitable, it will happen
Economists are very good at saying that something cannot go on forever, but not so good at saying when it will stop.