NEMA’s shipment index for sodium vapor high intensity discharge (HID) lamps increased 7.1 and 2.0 percent on a quarterly and year-over-year basis, respectively, during Q3 2011. However, metal halide lamps decreased by 5.3 percent from the previous quarter. The index for mercury vapor lamps decreased too, falling by 0.6 percent - erasing gains during the previous quarter. Moreover, the mercury vapor index posted a double-digit decline of 19.4 percent on a year-over-year basis.
 
Variations in market share were concentrated in sodium vapor and metal halide lamps. Sodium vapor lamps increased by 2.7 percent to 34.4 percent, while the market share of metal halide lamps decreased to 60.9 percent. The market share of sodium vapor lamps remained unchanged at 4.7 percent.