Most Americans would rather keep wealth to themselves than help others

Also, when people and institutions give to charity, there is sometimes a political or even financial incentive to do so. For instance, some charities (like the Peace Corps) have been accused of spying for their governments, and others like the Bill and Melinda Gates Foundation have been accused of being used to funnel money to large corporations. In both cases, the underlying motivation for donations could be more about helping the people giving the money than about helping others in need. Without such motives, it's possible that not nearly as much money would be given.

In the experiment the article is about, however, such political and financial incentives didn't exist. It was purely about giving money to others without any conceivable benefit to oneself. Thus, it could be a better gauge of an actual urge to help others motive without any recompense than charitable giving in the real world is.

Though, if you look at the "most charitable" report, I can't find where they found the countries ranked by GDP. Additionally, the report does show that the USA has the second most total people donating, but only ~43% of the population donating. So both could be true.

The way you're reading it, there are three different amounts: three potential amount for each of two cards.

But it's perfectly correct to read it as there being only two different amounts: one final, chosen amount for each of two cards.

There is a countering effect where inequality is a needed byproduct to incentivize people to, for example, start businesses. This is also obviously true in general.

The question is where these two curves intersect, I. e. whee the benefits are no longer enough to compensate the loss from unequal distribution.

It seems likely that the US is long past this point at least in gerade to the compensation of lawyers, top executives, or stock traders. After all, these professions also exist in more equal societies and there’s no reason to believe people cut out to be high-charging CEOs in those countries choose to become couch potatoes and leave the $15,000,000 job to lesser individuals because they require $150,000,000 to even bother.

On the startup side it’s a little more murky. But keep in mind that almost all startup founders come from the financial security of an upper-middle class family, and even in the US, the success of a Silicon Valley is rather unique. It may be easier attributed to network effects, excellent universities, the status of the English language, or the availability of capital.

Wikipedia has this summery with some empirical evidence:

Effects of inequality researchers have found include higher rates of health and social problems, and lower rates of social goods,[112] a lower level of economic utility in society from resources devoted on high-end consumption,[113] and even a lower level of economic growth when human capital is neglected for high-end consumption.[114] For the top 21 industrialised countries, counting each person equally, life expectancy is lower in more unequal countries (r = -.907).[115] A similar relationship exists among US states (r = -.620).[116]

2013 Economics Nobel prize winner Robert J. Shiller said that rising inequality in the United States and elsewhere is the most important problem.[117]

Increasing inequality harms economic growth.[118]

The economic stratification of society into "elites" and "masses" played a central role in the collapse of other advanced civilizations such as the Roman, Han and Gupta empires.[119]

https://en.wikipedia.org/wiki/Economic_inequality#Effects

I'd rather visualize it as a line going from left to right, that curves upward as it goes to the right. A Gini-0 would be horizontal, a Gini-1 would basically be a hockey stick. So the US is generally going to be steeper on the right side than Denmark, but in reality each region's line is going to have a bunch of wiggles.

So I wonder if there's an ideal "line". Either scored by some metric, like at what point does some measure of mobility or entrepreneurship increase or decrease... or some measure of system stability.

For instance, I've seen a few references that the value of money is roughly logarithmic as it increases. If every wealth holder were taxed logarithmically (so that the tax bill "hurts" everyone equally), and the proceeds were then distributed to everyone equally, would that push the line to some sort of stable shape, no matter how unequal the system starts?

If so, you could consider that a line of capitalism, with anything on either side being disproportionate in some way. The line should still curve since talent/skill/etc will always have an impact.