The income gap in the U.S. continues to grow and a major reason is the pay of the poorest sector, which is on a downward spiral, according to an Associated Press report from CNBC.

The news outlet said that the most impoverished households are still struggling with only a fraction of their earnings since the Great Recession began in 2007. An analysis of Census data released by Brookings Institute revealed the decrease in income of the bottom 20 percent in New York City, New Orleans, Cincinnati, Washington and St. Louis.

Alan Berube, a senior fellow at Brookings and deputy director of the metropolitan policy program, explained that the widening gap highlights the declining salary of the lowest sector.

"It's really about the poor losing ground rather than these upper-class households pulling away," Berube said.

One example that illustrated the findings was the situation in Cincinnati, where the bottom 20 percent raked in $10,454 in 2014, which is 3 percent less than their earnings in 2013 with inflation. On the other hand, their top 5 percent earned at least $164,410 in 2014, showing an increase since 2013.

On a national level, the top 5 percent earned 9.3 times than the bottom 20 percent, which is the same number as in 2013 but significantly lower than the pre-recession ratio of 8.5.

Boston reportedly marked the biggest income disparity as its top 5 percent earned 17.8 times of the bottom 20 percent's salary. It's followed by New Orleans, Atlanta and Cincinnati. Utah showed better conditions with a low 7.8 ratio, as well as Denver where improvements were marked.

Housing has also proved to be a problem across the country as rent takes up a bigger cut from the income of the average American. The study by Brookings showed that the bottom 20 percent in Washington D.C. are forced to shell out half of their earnings on rent.

Harvard's Joint Center for Housing Studies conducted a separate study in December that confirmed this phenomenon as they revealed that between 2001 and 2014, the average rent cost hiked 7 percent and income dropped 9 percent, with inflation adjusted.

In a summary of their study at City Lab, authors Berube and Natalie Holmes reiterated the increase of top incomes and decline of the poorer sector in metro areas adding, "Indeed, double-digit slides in 20th percentile incomes were quite common across large metro areas. High-income households earned significantly less in 2014 than in 2007 in 33 of the 100 largest metro areas, but the same was true for low-income households in fully 81 of those metro areas."