Very true, poverty and lifespan, litteracy… more or less all of the blue indicators (crime…) would set a “state of the country”, pondered by the "everyone"s opinion.
Basically, how does the game knows how the “global economy” is doing, each turn? Boom, stable, recession… it changes, our country has got no impact on it, and it has got an impact on our country.
Using the same system, if you take “world average”, each turn its indicators (the same as our blue ones) would change (partly influenced by foreign aid, boundaries controls, import taxes…). Then, two strategies:
-All these indicators are combined to make a total score (human development indicator or whatsoever), and each turn our HDI is compared to the world average. If higher, our population is proportionnally happier. If lower, our population is proportionnally… well you get it.
-There is this big indicator, yes, but the componants are also compared one by one, and affecting the related population segments. So you can have your country have a high HDI, making people happy. But then, your poverty is actually way over the average world rate and then the poor population is unhappy of that fact.
The second solution is probably more complexe, but it brings more. You may think you treat well your socialists, and in the present game it would be the case… but actually you’re far behind! And then, the socialists, despite their good treatement, are unhappy
Also, it brings more possibilities of events (demonstration from the ecologists because our country is one with the most pollution in the world, nobel prize of peace because we’re giving so much foreign help - this prize would raise the national pride and then make the patriots feel a tiny bit better about it, requests to share our technological advance with the rest of the world…).
So to put it more clearly:
“But what would be the inputs/influences that affected it?”: All the blue indicators, themselves being compared to the “average world” blue indicators (that would have to be created and to evoluate a bit as the global economy… I would even say that one could influence the other).
“You could get events that said other countries were doing really well or badly, which would decrease or increase the value respectively”: Very true, and require more investment or less investment to stay ahead of the race. You can also have messages like “country x has suffered a major earthstrike, would you like to send help”… if yes, better reputation, but if not, of course, it decreases the average world HDI and puts you in a better place…
“Foreign aid could actually decrease the value, because it means that other countries will start doing better”: Yes, that’s very true.