A national campaign for electronic health records is driving business for at least 20 companies with thousands of workers ready to help stressed doctors log the details of their patients' care — for a price. Nearly 1 in 5 physicians now employ medical scribes, many provided by a vendor, who join doctors and patients in examination rooms. They enter relevant information about patients' ailments and doctors' advice into a computer, the preferred successor to jotting notes on a clipboard as doctors universally once did. The U.S. has 15,000 scribes today and their numbers will reach 100,000 by 2020, estimates ScribeAmerica, the largest competitor in the business. After buying three rivals this year, it employs 10,000 scribes working in 1,200 locations.