NEMA’s sodium vapor high intensity discharge (HID) lamps shipment index declined for the fourth consecutive quarter on a year-over-year basis, retreating 15.8 percent during Q2 2011. The index value of 77.7 is the lowest reading on record for the series. Mercury vapor and metal halide HID lamp indexes performed better during the quarter, increasing 2.5 and 2.3 percent, respectively, compared to the same period last year.  
 
Market shares of the three HID lamps types varied by less than 1.0 percentage point compared to the previous quarter. Metal halide lamps continued to dominate the HID market with a share of 63.9 percent. Sodium vapor lamps decreased by 0.9 percentage points to 35.1 percent. Mercury vapor lamps garnered a 4.7 percent share, an increase of 0.2 percentage points.