The Philadelphia middle class, a backbone of economic vitality that once made up the majority of residents in most of the city’s neighborhoods, has declined in steep numbers since 1970, from 59 percent to 42 percent by 2010, according to a report released Monday, the first of its kind.

The precipitous decline of adults within this long-celebrated class occurred widely across the city and most sharply before 2000, sparing only chunks of Far Northeast Philadelphia and Roxborough and smaller pockets elsewhere. Those areas remained majority middle-class as of a few years ago, said the Pew Charitable Trusts, which spearheaded the study.

The data capture what has been sensed and dreaded by policymakers for years: Philadelphia is decidedly poorer than when it was a manufacturing powerhouse, losing even a greater share of higher-taxpaying middle-class residents than the nation as a whole, and failing even to see increases in its upper-class population to match other cities that fared better.

Whether middle-class Philadelphians fell into a lower-income class, moved into the suburbs, or died is not shown by Pew’s analysis, as researchers have found such detailed tracking to be elusive.

Marriage an overlooked component to income inequality
But the share of lower-class Philadelphians spiked from 30 percent […]