Genesis 41:34

Let him appoint officers to take up a fifth part Not by force or violence, but by purchase at the common price, which would probably be very low during these years of plenty. But why only a fifth part, seeing the years of famine were to be as many as the years of plenty? 1st, Because people would live more sparingly in the time of the famine. 2d, It is likely that many persons, in all parts of the country, besides the king, would lay up great quantities of corn, both because they could not easily consume it all, and in expectation of a time of greater scarcity and dearness, when they might either use it themselves, or sell it to their advantage. Add to this, 3d, That even the fifth part of the produce of those years of plenty might be more than the half, yea, equal to the whole crop of ordinary years.