The diagram above shows the number of households in the United States based on their annual income from 2007 to 2015. There are four categories of annual income. The lowest income is less than 25 thousand dollars, followed by 25 to 50 thousand dollars, and then middle income is around 50 to 80 thousand dollars, upper middle income starts from 75 to 100 thousand dollars, and the highest income starts from 100 thousand dollars.
The number of people that had the lowest income increased in the year 2011 and decreased in 2015, it goes the same with the people who have salaries around 25 thousand dollars to 50 thousand dollars. The number of people with middle-income salaries from 50 to 75 thousand dollars remains stagnant. Compared to the number of people with upper-middle salaries has fluctuated but has not significantly increased. And the number of people with the highest income declined from 2007 to 2011, but then increased drastically from 2011 to 2015.
The graph also shows that, people with the highest income had been dominated from 2007 but decrease slowly until the year of 2011. It might be due to the financial crises that happened in the United States in 2008. In 2015, the United States was dominated again with high income people.