The product of a group of people is a function of the characteristics of the people. This is just a simple fact.

Some people confuse themselves by pointing to education as a contradiction to this. They say that the presence of education changes the product of society, so it's not just the inherant intelligence of people that matters. This is incorrect because as I stated, it is the characteristics of people that matter and education has the effect of improving characteristics. It is the end result of both nature and nurture that then determines how well a society fares. People who have good "nature" are required though, because they end up doing well regardless of education level whereas naturally dumb people need to be force fed an education which leads to a fragile system where any lapse in educational infrastructure leads to prolonged slump in society overall.

There are complicating factors that make my initial observation difficult to find. Power and influence over the product of society is not evenly distributed over the population. This just means you need to take an integral over the influence levels -- if all of the power is in the hands of very intelligent people then everything will be ok even if there are mobs of stupid people. There are many examples of this.

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Look at gun rights. If we abstract away the gun we can see that it is really responsibility that is being talked about. Is the population up to the task of owning guns without killing other people? This is not very different from the responsibility to own a car or powerful cleaning chemicals or knives or a million other things, or even the vote. Guns happen to be perhaps one of the most damaging rights in the short term. But I no longer ask whether or not people are ready for guns because if they are not ready for guns they are not ready for the vote or the car or raising children. The result I have come to is that everyone in society needs to be up to the task of having responsibility because if they aren't, the country will collapse. Taking away the guns will stop deaths but it won't solve the root of them problem and it won't stop the slow death of the country.

I think that is probably the biggest theme of my idea. Slow, subtle changes that are difficult to attribute to anything are actually influenced by a very simple thing. Lack of good characteristics will result in a slow and nebulous death manifesting itself as failures of institutions and other things. Injecting good characteristics via education, culture or immigration results in fantastic progress in prosperity and quality of life -- all looking like good luck or a magical combination of law and infrastructure.

Edit

And I have to add that there are countless examples everywhere you look. News for example: people blame news companies for publishing misleading, fake, distasteful, etc stories but really it's the people consuming the news who are at fault. If nobody bought or watched that kind and of news then it wouldn't be published. And there are endless examples like that. Most things that are a national embarrassment like that are a result of the people in general supporting it or being apathetic to it.