There's a staggering amount of misunderstanding surrounding IQ, which is why there's often a corresponding hostility towards statistics drawn from IQ.
The main thing to keep in mind is this: the metric of IQ is useless as an absolutely accurate predictive tool when applied individually, but is statistically proven as an absolutely accurate predictive tool when applied to large populations. In other words: if you show me a single individual with an IQ of 130, I cannot definitively say that he will be more successful in life (meaning: higher earning, healthier, less criminally inclined, etc...) than another individual with an IQ of 90. However, if you give me a sample of 1,000 people with IQs of 130 versus 1,000 people with IQs of 90, I can statistically guarantee that the sample of people with 130 IQs will on average be more successful. This is not up for argument. This is not my opinion. This is literally as statistically sound as stating, "An average sample of 100 NFL players will be more athletic than a sample of 100 random Americans."
We don't really know what IQ (also called g for "general intelligence") actually is. We just know that we can sort of measure whatever "it" is with carefully designed tests, and that people who excel at these tests tend to excel in other areas of life that demand cognitive capacity. This phenomenon has been observed repeatedly in thousands of studies, across all cultures and races. Higher IQ, on a population level, always correlates with improved life outcomes. But again, it bears repeating that an individual IQ score is not determinative of anything. It's simply a measurement of how well the person did on an IQ test. We can make predictions based on statistical correlations that we know exist, but statistics also tell us that outliers exist. There are plenty of 90 IQ millionaires walking around. Some people beat the odds, or simply possess other traits that compensate for IQ. If you're 7 feet tall and 300 lbs. of solid muscle, you can probably find a way to leverage those traits to become successful. If you've got an utterly magnetic personality, the world is your oyster. Conversely, there's no shortage of people with 130+ IQs who are total failures, who never took advantage of their intelligence (and who are smart enough to recognize and lament this fact, and become extremely embittered as a result).
People need to stop being offended by discussions of IQ. These statistics aren't personal. No one is talking about you. These are statistical correlations drawn from large population data. If I tell you that men over 6'5" tall are wildly overrepresented in the NBA and you shout out "BUT WHAT ABOUT MUGSY BOGUES MAN!" then you're committing the same error many people do with IQ. Remember, IQ predictions can only be drawn with 100% accuracy across populations. Individually we can make only rough predictions based on IQ. Outliers and exceptions always exist in both directions (i.e. the 90 IQ millionaire and the 140 IQ virgin drug addict living in his mother's basement).
