Paradox of thrift
It is a kind of prisoner's dilemma: saving benefits each individual but damages the general population. This is a paradox because it is contrary to intuition. Someone might think that what seems to be good for an individual in the economy will be good for the entire population. However, exercising thrift may be good for an individual by enabling that individual to save for a "rainy day", and yet not be good for the economy as a whole.