"People are getting dumber. That's not a judgment; it's a global fact."

Evan Horowitz examines the global phenomenon of declining IQ scores.

For a while, rising IQ scores seemed like clear evidence of social progress, palpable proof that humanity was getting steadily smarter — and might even be able to boost brainpower indefinitely. Scholars called it the "Flynn effect," in homage to J.R. Flynn, the researcher who recognized its full sweep and import.

These days, however, Flynn himself concedes that "the IQ gains of the 20th century have faltered." A range of studies using a variety of well-established IQ tests and metrics have found declining scores across Scandinavia, Britain, Germany, France and Australia.

Details vary from study to study and from place to place given the available data. IQ shortfalls in Norway and Denmark appear in longstanding tests of military conscripts, whereas information about France is based on a smaller sample and a different test. But the broad pattern has become clearer: Beginning around the turn of the 21st century, many of the most economically advanced nations began experiencing some kind of decline in IQ.

One potential explanation was quasi-eugenic. As in the movie “Idiocracy,” it was suggested that average intelligence is being pulled down because lower-IQ families are having more children ("dysgenic fertility" is the technical term). Alternatively, widening immigration might be bringing less-intelligent newcomers to societies with otherwise higher IQs.

However, a 2018 study of Norway has punctured these theories by showing that IQs are dropping not just across societies but within families. In other words, the issue is not that educated Norwegians are increasingly outnumbered by lower-IQ immigrants or the children of less-educated citizens. Even children born to high-IQ parents are slipping down the IQ ladder.

Some environmental factor — or collection of factors — is causing a drop in the IQ scores of parents and their own children, and older kids and their younger siblings ... Ultimately, it’d be nice to pin down the precise reason IQ scores are dropping before we’re too stupid to figure it out, especially as these scores really do seem connected to long-term productivity and economic success.

There's more at the link.

I'd like to suggest three factors:

1. The decline in standards of education.  In too many First World nations, education now consists of focusing on feelings and groupthink, rather than facts and individual effort.  "Tall poppy syndrome" appears to be in effect, where outstanding scholars are actively discouraged from proceeding as fast as they're able;  and shamed into hiding their talent so as to be more socially acceptable to their less bright peers.  There's also too much emphasis on politically correct shibboleths du jour, rather than the three R's and other fundamental areas.  (I can still remember being forced to learn my multiplication tables in primary school, and getting my knuckles rapped - literally, with a heavy ruler - whenever I got them wrong.  It's basic mathematical knowledge that has stood me in good stead every day of my life.  I'm baffled by today's kids, who have to reach for a calculator - or the calculator app on their smartphones - when faced with basic arithmetical problems like that.)
2. The over-reliance on technology.  Smartphones, tablets, personal computers and the like have made it trivially easy to look up almost anything, anywhere, at any time.  There's no sense of the need to internalize knowledge, to make it part of oneself.  Even worse, kids aren't taught how libraries and reference indices work.  I can remember hours spent going through card index drawers, researching projects and looking for sources.  (Heck, I was chief librarian at my high school - keeping the index properly organized was part of my job!)  Kids today wouldn't even know where to start looking for that stuff, if their electronic aids were suddenly shut down or taken away.  I think that's a serious drawback.
3. The lack of education in how to think logically and rationally.  I think a basic foundation in philosophy, logic, reasoning and applying one's mind to problems is a fundamental need that underlies and empowers almost every other aspect of education.  (For example, I was pretty hopeless at mathematics until I was introduced to a short book called "First Steps in Logic".  It analyzed arguments by reducing them to symbolic logic form, and applying strict rules of reasoning.  Suddenly, math [which is nothing more than a series of logical operations on numbers and formulae] made a whole lot more sense.  I went on to apply the same basic rules to designing computer programs in my early 20's.  Philosophy and logic weren't outdated at all, but fundamental to my early success.)

Those are my primary guesstimates, anyway.  I'm sure readers can contribute their own insights.

I don't think IQ is so much declining as being "dumbed down" by an education system that discourages intellectual curiosity and personal growth in favor of communal touchy-feely mind-gropery and political correctness.  Get rid of the latter, and you'll solve the former.  Leave the latter in place, and the former will only get worse.

Peter