The bar chart illustrates the number of US households, in millions, categorized by annual income in 2007, 2011, and 2015.
Overall, households earning less than $25,000 consistently accounted for the largest share, while those earning $100,000 or more increased steadily over the given period. Meanwhile, the middle-income groups ($25,000-$74,999) generally declined.
In 2007, the number of households earning below $25,000 was around 30 million, making it the highest category. This figure remained nearly unchanged by 2011 and rose slightly to about 32 million in 2015. By contrast, households in the $25,000-$49,999 bracket dropped from approximately 29 million in 2007 to around 27 million in 2015. A similar downward trend is seen in the $50,000-$74,999 group, which decreased from about 25 million to nearly 23 million during the same period.
On the other hand, the proportion of households in the $75,000-$99,999 category remained stable at roughly 15 million across all three years. Notably, the number of households earning $100,000 or more rose significantly from about 25 million in 2007 to nearly 30 million in 2015, becoming the second-largest group by the end of the period.
In summary, while the lowest- and highest-income groups expanded, middle-income households declined over time, reflecting a polarization of income distribution in the US.