CHARLESTON, W.Va. -- The income gap between West Virginia's richest and poorest residents has widened dramatically over the past few decades, according to a study by the Economic Policy Institute and the Center on Budget and Policy Priorities. West Virginia had the seventh-largest increase in income inequality in the nation between the late 1970s and the mid-2000s, according to the study by the nonprofit and nonpartisan research organization. It found that in the mid-2000s, the richest 20 percent of families had an income of $134,464 per year. That's 8.4 times greater than the poorest 20 percent, whose average yearly income was $15,917. In the late 1970s, the ratio was 4.9. Stuart Frazier, a policy analyst for the West Virginia Center on Budget and Policy, called the trend "extremely troubling.''"Growing up in poverty is harmful to our state's children and affects everything from their performance in school to their earnings as adults,'' Frazier said in a news release Thursday. Nationally, the average income of the richest fifth of households was eight times that of the poorest fifth as of the late 2000s. According to the report, New Mexico, Arizona, California, Georgia, New York, Louisiana, Texas, Massachusetts, Illinois, and Mississippi face the largest gaps. The study was based on inflation-adjusted U.S. Census data. The group said the study is one of the few to examine income inequality at the state level. It measured and compared income trends among the highest-, middle-, and lowest-income families in four periods -- the late 1970s, the late 1990s, and the mid- and late 2000s.