Are you really that misinformed? Decline? Have you not heard about the Flynn-effect?

Also:

"The level of intelligence, in other words the Intelligence Quotient, is always a comparison with the sample or group of individuals that took part in the creation of the test and is therefore always a relative measurement."

and

"Average IQ of a group is always 100"

https://www.brain-testing.org/intelligence-quotient-iq