lamps for "crime fighting", a marketing strategy that backfired when cities such as Newark and New Orleans rejected sodium vapor, to avoid publicly stigmatizing high-crime neighborhoods. When the availability of high-pressure sodium vapor lamps coincided with the rise of social unrest in the mid-1960s, lamp manufacturers once again promoted the potential for sodium vapor lighting to enable better street surveillance. High-pressure sodium lamps produced a distinct "yellow/orangeish light", brighter than mercury vapor light, which has been described as a "harsh metallic blue" in hue. During the OPEC oil embargo, Mayor Richard J. Daley announced a plan to make Chicago "the first large U.S. city to have sodium vapor lamps on all residential streets", replacing 85,000 mercury vapor streetlights. Although a December 1973 article in the Chicago Tribune was optimistic about the "more cheerful, brighter, gold-colored vapor lamps", the newspaper's own architecture critic worried about the "eerie, ominous quality of sodium vapor illumination". In 1976, the large-scale installation of sodium vapor lamps began on Chicago's arterial streets. In the end, the most critical factor in favor of sodium vapor lamps was their cost. In 1980, the annual operating cost for the average incandescent lamp was $280; for mercury vapor lamps, it was $128; and for low-pressure sodium vapor lamps, it was $60 a year. Meanwhile, high-pressure sodium vapor lamps cost only $44 a year to operate, with a standard life expectancy of 15,000 hours, which also helped to lower labor and maintenance costs. According to the Edison Tech Center, sodium vapor lamps are "the most ubiquitous lamp for street lighting on the planet." Light emitting diodes In recent years, efforts to make street lighting more energy efficient have focused on using light-emitting diodes (LEDs) to replace high-pressure mercury (HPM), metal halide (MH), and high-pressure sodium (HPS) luminaires. LEDs also produce a whiter light, and can be installed as part of a centrally managed system with further energy saving controls, such as part-night lighting and dimming. Although the up-front costs of installing LED fixtures is significant, municipalities switching to LED street lighting generally expect to recoup their investment through reductions in ongoing electricity and maintenance costs. Many of the early projects in the United States also benefitted from economic stimulus block grants. In 2007, the city of Ann Arbor, Michigan, announced plans to become "the first US city to convert all of its downtown streetlights to LED technology." The city replaced 120-watt