THE progressive reformer and eminent jurist Louis D. Brandeis once said, “We may have democracy, or we may have wealth concentrated in the hands of a few, but we cannot have both.” Brandeis lived at a time when enormous disparities between the rich and the poor led to violent labor unrest and ultimately to a reform movement.

Over the last three decades, income inequality has again soared to the sort of levels that alarmed Brandeis. In 1980, the wealthiest 1 percent of Americans made 9.1 percent of our nation’s pre-tax income; by 2006 that share had risen to 18.8 percent — slightly higher than when Brandeis joined the Supreme Court in 1916.

Congress might have countered this increased concentration but, instead, tax changes have exacerbated the trend: in after-tax dollars, our wealthiest 1 percent over this same period went from receiving 7.7 percent to 16.3 percent of our nation’s income.

What we call the Brandeis Ratio — the ratio of the average income of the nation’s richest 1 percent to the median household income — has skyrocketed since Ronald Reagan took office. In 1980 the average 1-percenter made 12.5 times the median income, but in 2006 (the latest year for which data is available) the average income of our richest 1 percent was a whopping 36 times greater than that of the median household.