(5/17/2013, 2:25 p.m.)  --  There is a David-versus-Goliath perception that makes many primary care physicians dealing with giant hospitals and health care systems feel disadvantaged during payment negotiations, but the truth is that every health system needs a strong primary care base. Now, more than ever, we can prove it. Merritt Hawkins, the national physician search firm, periodically surveys hospital chief financial officers about how much revenue physicians in 18 different specialties generate for their affiliated hospitals each year. For the first time since the survey started in 2002, the CFOs indicated in a report released this month that primary care physicians generate more revenue, on average, than subspecialists. More