Median income is the amount that divides the income distribution into two equal groups, half having income above that amount, and half having income below that amount. Mean income (average) is the amount obtained by dividing the total aggregate income of a group by the number of units in that group.
In 2013, Gallup published a list of countries with median household income, based on a self-reported survey of approximately 1000 adults from each country. Using median, rather than mean income, results in a much more accurate picture of the average income of the middle class since the data will not be skewed by gains and abnormalities in the extreme ends. The figures are in international dollars using purchasing power parity and are based on responses from at least 2,000 adults in each country, with the data aggregated from 2006 to 2012. Below is a list of the top 30 countries. The figures are before deduction of taxes and social contributions and not adjusted for household size.
Based on analysis on US median household income, median household money income during the 2006-2012 period averaged $53,836, therefore by comparison the Gallup result is underreported and is even below the Census' own figures. A study on the Census income data showed that when correcting for underreporting, US gross median household income was $58,997 between 2006 and 2010 (table 3). 
The annual median equivalence disposable household income for selected countries is shown in the table below. This is the disposable income of an equivalent adult in a household in the middle of the income distribution in a year.
Based on analysis of the CPS data, US median household income has been consistently under-counted by a ratio of 83-85% (mean undercounted by 75%). Other analysis has shown varying rates of quality among countries; For example, Norway, Sweden, Denmark, Netherlands, Germany, Austria, and UK all captured 85% or more income as compared to the national accounts (details in link--Appendix 4).
This graph shows the income of the given racial and ethnic groups, in 2014 dollars.
Since 1980, U.S. gross domestic product (GDP) per capita has increased 67%, while median household income has only increased by 15%. An economic recession will normally cause household incomes to decrease, often by as much as 10% (Figure 1).
Median household income is a politically sensitive indicator. Voters can be critical of their government if they perceive that their cost of living is rising faster than their income. Figure 1 shows how American incomes have changed since 1970. The last recession was the early 2000s recession and was started with the bursting of the dot-com bubble. It affected most advanced economies including the European Union, Japan and the United States.
The current crisis began with the bursting of the U.S. housing bubble, which caused a problem in the dangerously exposed sub prime-mortgage market. This in turn has triggered a global financial crisis. In constant price, 2011 American median household income is 1.13% lower than what it was in 1989. This corresponds to a 0.05% annual decrease over a 22-year period. In the mean time, GDP per capita has increased by 33.8% or 1.33% annually.
A comparison between Median Equivalised Household Income and GDP per Capita in USD for select developed countries is shown in the chart below.