The rule might feel true as a consequence of Zipf's law that says the second biggest is roughly half as big, and the third biggest is 1/3 as big as #1, etc. So

The rule might feel true as a consequence of Zipf's law that says the second biggest is roughly half as big, and the third biggest is 1/3 as big as #1, etc. So because of a power law, the #1 and #2 are big enough that many people will just dismiss the rest.