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Political leaders want to stay in power. According to one of the most important theories of political science, The Selectorate Theory, to maintain power politicians will balance their resources between public goods (e.g. rule of law, clean air, free trade) or private goods (e.g. bribes and monopoly rights), where public goods are defined as goods that are indivisible and that you cannot exclude any individual from their benefits. If the amount of people the political leader needs to maintain power is small, they can provide private benefits for these supporters (Bueno de Mesquita et al, 2003), like autocracies often do. For example, one of the main reasons holding Africa developments is that their politicians redirect taxes from the mostly rural population to provide benefits to the urban elites who have a bigger say in choosing the political leaders, making the rich get richer and the poor get poorer (Bates, 1981). On the other hand, in democracies, usually, that happens less often because political leaders depend on a greater number of supporters for political survival. Hence, it becomes too expensive to please everyone with actions like bribes and monopoly rights. In democracies, on average, politicians must rely more on the policies that make the society better off as a whole, like strengthening rule of law and encouraging free trade (e.g. Milner and Kubota, 2005). Income inequality becomes a major problem when leaders manage to maintain power by only pleasing a few people, although everyone has one vote. There are significant indications that this is happening in the USA.
American elections are the most expensive in the world and political candidates who spend more money in their campaigns tend to be elected. In the US 2000 election, for example, the average lower house winner spent almost $850 thousand in the campaign and the average loser spent around $300 thousand. In the higher house, the same pattern happened. The average winner spent over 7 million dollars, while the average loser spent less than 4 million dollars (Graetz and Shapiro, 2005). Moreover, the people who finance political campaigns are mostly rich individuals/corporations looking for lobbying interests since the US has almost no constraint on how much can be spent or who can finance political campaigns. More than 40 percent of the US campaign funding comes from 0.01 percent of the wealthiest individuals in society (Bonica et al., 2013). The US resembles more a "one dollar one vote" system than a “one person one vote” one (Stiglitz, 2012). If income inequality is large enough that a small number of people can make a leader stay in power, then you can have a "captured democracy," i.e. the de facto power in society suppressed de jure power influence of institutions (Acemoglu and Robinson, 2008). In other words, you can be working, paying to tax, but most of the benefits go to the rich. That is, you are pretty much a slave. You are on the road to serfdom (See Where is the land of opportunity?).
According to the University of California at Berkeley Professor Gabriel Zucman, "in 1980 the average income of the bottom 50% in the USA was 16,000 dollars. In 2018, the real average annual income for this bottom 50%, i.e. after adjusting for inflation, is still 16,000 dollars. [...] So, although the US continued to grow all this growth has been taken by the top half. The bottom half of the American population has been shut off from economic growth in the last 30+ years." In fact, from all wealth produced from 1980 to 2016 in the world, the 1% richest people have taken twice as much of that growth than the world’s bottom 50% (Alvaredo et al, 2018). Moreover, the US has been moving away from public goods to private goods, like creating international trade barriers, distributing monopoly rights, eroding its rule of law (e.g. Stiglitz, 2012). As Nobel Laureate Joseph Stiglitz and other top scholars (Chetty et al, 2014) have shown, the American Dream is dead.
How to fix this? The captured democracy phenomenon is a political problem that can be caused and reinforced by economic inequality. However, there is no empirical evidence of a country as unequal as the US becoming very equal by lifting the poor. In the last 5000 years, all successful movements toward equality happen through mass warfare, complete revolutions, state collapse, and catastrophic plagues (Scheidel, 2017). There is no clear evidence of why the US should be an exception. Taxing the rich, which is virtually impossible, is not necessarily going to help decrease inequality nor the creation of major wealth redistribution programs. Thus, major changes should be made on political institutions in which elections cannot really help. If income inequality and lack of freedom deeply bothers you, the data says that your best bet is to move abroad and renounce your citizenship.