As an aside, the mistake in nutrition was simply that it wasn’t true. And it also wasn’t a “mistake,” it was a lie that the sugar industry paid to spread.
if you pick n numbers at random, it's not likely that one of them is bigger than the half of their sum.
but my intuition says that if you pick all variables from the same distribution, this should still hold.
At first, we don't know anything about the factors, so they are assigned a random importance. or am I missing something?
What's missing here are facts.
To dismiss something based on something anecdotally unrelated seems short-sighted.
I happen to believe peer groups are really important. But other things are important, too, including the adults.
Remove all the middle-aged and older men from a city, but still provide other necessities, and you'll see some terrible outcomes. (This is true in other species as well, like elephants where older males are hunted for tusks.)
A dominant factor can also only account for less than half of an explanation if there are enough factors. E.g. Peer group is 40%, parents are 30%, teachers are 20%, TV/videogames/groups-seen-but-not-interacting-directly-with 10%. Here peer groups would still be dominating but parents and teachers are significant factors as well. These percentages are close enough that it would be ridiculous to just focus on one (or even the first two alone).
We all have stories about a great teacher or a terrible parent. But these are anecdotes. You don't actually know what would have happened if you had different parents, or different friends, or went to a different school.
It's perfectly possible that if circumstances were different, you would have gotten to the same place, by a superficially different path.
The specific stories would vary, of course. But when we talk about society-level policy, it's not specific personal stories that we focus on. It's things like income, marital status, job field, health, criminality. A lot of evidence suggests that even if your specifics were very different you would have actually ended up largely in the same place on these metrics.
Yes, it’s all of them. And they all need to be addressed instead of trying to pick the one all-dominant factor.
> ... these are anecdotes.
Combine a lot of anecdotes and add in more scrutiny and we can call that data.
IMO this no longer holds true with the advent of the internet era. You're now spending equal amounts of time exposed to a countless number of people. Even if you aren't physically with them, and even if it's a one-way relationship (i.e. they are not aware of your observance and existence), they are still influencing who you are.