Over the past 30 years, middle-class jobs shrank from 75 percent to 68 percent of the U.S. workforce. Meanwhile, job growth shifted to high-paying jobs requiring a lot of education — such as legal, engineering and technology industries — and low-paying jobs requiring little schooling, such as food preparation, maintenance and personal care. A new Federal Reserve Bank of New York report warned that the middle-class consumer base that historically powered America’s economy is beginning to erode.