Don't believe those numbers. An IQ of 70 is one of the symptoms of mental retardation. Source: https://www.ncbi.nlm.nih.gov/books/NBK332877/

Since IQ occurs on a bell curve, if the 50 percentile occurs at IQ 70, then half of them are below that number and thus suffering from mental retardation (1 in 2). This number does not meet anyone's real life experience with Black people.

These numbers are probably based on Richard Lynn's work. You'll be laughed at by psychometricians if you were to employ the methods he did in his work to determine a country's IQ. Even the relation of IQ to intelligence is debated, though IQ does correlate with many things that are socially considered to be "successes".

If you insist, keep in mind this same work also shows white people are "inferior" to Asians in terms of "IQ".