How much better are doctors in groups doing?
D003625:Data Collection; D004470:Economics, Medical; D006123:Group Practice / Q000191:economics*; D006125:Group Practice, Prepaid / Q000191:economics; D007182:Income; D011331:Private Practice / Q000191:economics; D011364:Professional Practice / Q000191:economics*; D013223:Statistics as Topic; D014481:United States