Based on the similar shifts underway the nation's economy after 1960, Philadelphia experienced a loss of manufacturing companies and jobs to lower taxed regions of the USA and often overseas. As a result, the economic base of Philadelphia, which had historically been manufacturing, declined significantly. In addition, consolidation in several American industries (retailing, financial services and health care in particular) reduced the number of companies headquartered in Philadelphia. The economic impact of these changes would reduce Philadelphia's tax base and the resources of local government. Philadelphia struggled through a long period of adjustment to these economic changes, coupled with significant demographic change as wealthier residents moved into the nearby suburbs and more immigrants moved into the city. The city in fact approached bankruptcy in the late 1980s. Revitalization began in the 1990s, with gentrification turning around many neighborhoods and reversing its decades-long trend of population loss.

What was the historical economic base of Philadelphia?