The Flynn Effect, where the average IQ in a country, this being pretty much every country that’s been doing standardized IQ testing, appears to be increasing as time goes on. Not the average IQ applied across people, but the average IQ applied across age groups.
That is, testing in one year a bunch of teenagers nets you a particular average score, and another group of teenagers in the same schools 15 years later a higher score, and the same in the next 15 years with yet another group of teenagers.
Which all is easily explained by, you’ve been teaching kids the things they need to know to do better on these tests than their older siblings/cousins did. Not that anyone is getting smarter, that they are instead just better trained for the task put in front of them.
By the way, the vast majority of standardized IQ tests have only one advantage, that they are standardized, which makes them excellent for testing for particular aptitudes relating to the test material and the way the test is carried out. Most standardized IQ tests are fairly quick, either done in less than half an hour in such a way that whole groups can be tested at once, to up to a couple of hours of individualized testing. I’ve had both, and both are just as meaningless. You want comprehensive testing that might tell you something, if and only if you know how to actually interpret the results? Try long term testing that takes hours in a day, and tends to run 3 to 4 days to complete all the testing. These though are often part of full scale psychological evaluations, rather than just testing IQ.