S.G.R. More than 99 percent of Americans have no idea what these three letters stand for. And yet they are extremely valuable: worth about $140 billion. This week, a House committee will finally take up the issue. The S.G.R., or the Sustainable Growth Rate formula, was enacted as part of the Balanced Budget Act of 1997 to restrain the inevitable increase in Medicare’s annual spending on physician services. … Nice idea in theory. Never worked out in practice (Dr. Ezekiel J. Emanuel and Topher Spiro, 7/29).