Believe it or not, it is possible for migration to take place between two countries so that the average intelligence of both countries, as measured by IQ, increases.
The conditions for this to happen are:
1. The average IQ of two countries A and B, are different.
2. The migrants must be below average intelligence for the country they are emigrating from, and above average in telligence for the country the are immiigrating to.
Example: Country A has three inhabitants with IQs 106, 108 and 110. The average IQ of the inhabitants of country A is 108. Country B has three inhabitants with IQs 88, 90 and 92. The average IQ of inhabitants of country B is 90.
The inhabitant of country A with an IQ of 1-6 leaves and goes to country B.
There are two inhabitants of copuntry A with IQs 108 and 110. The average IQ of inhabitants of country A is now 109.
There are now four inhabitants of country B, with IQs 88, 90, 92 and 106, The average IQ of inhabitants of country B is now 94
The average IQ of both countries has gone up, even though the average overall IQ has not changed, since the total IQ is unchanged.