What has happened is the average IQ has gone up over time (called the
Flynn Effect), meaning the various IQ tests have had to be re-calibrated over time. In effect, IQ tests have become harder, to balance out people tending to be better at what IQ tests measure. IQ largely measures abstract reasoning, which makes one wonder if people are functionally becoming more "N" over time.
Another implication of this is that people who had a certain IQ on a test twenty years ago may not score the same today, even if they are equally intelligent (in the sense that IQ measures). Also, IQ isn't necessarily static over the lifespan, so people's IQ scores can go up or down as they age.
It's also important to keep in mind that IQ measures a narrow band of intelligence. I think of someone like my dad, who isn't necessarily super mentally quick (though he's not slow), but who is amazingly self-disciplined and focused. He applies his intelligent much more effectively than many, and to greater results.