The chart illustrates the annual income of US households in five different groups in the year of 2007, 2011 and 2015.

It is clear that families who earned more than $100000 generally had the largest number among these five groups, with a significant increase in 2015, while income group of $75000 to $99999 remained the smallest part in the period.

The number of US households with more than $100000 rose from about 30 million in 2007 to 33 million in 2015, though dropped by around 2 million in 2011. Similarly, the number of households who earned less than $49999 showed a general increase. Populations of these two low-income groups both started at no less than 25 million in 2007, rose to less than 30 million in 2011 and declined slightly to about 28 million in 2015, as the number of households with $25000 to $49999 was bigger than the number of households with less than $25000 in the whole period.

In terms of mid-income families, the numbers of households earned $50000 to $74999 and $75000 to $99999 remained almost unchanged in the period. The figure of the income group with $75000 to $99999 fluctuated between 14 million and 15 million and ended at 15 million in 2015, while the figure of the lower income households almost remained the same at 21 million.