A 1994 EPA report provides the following information about the mercury-switch thermostat market.

"Analysis of thermostat markets indicates that approximately 10 to 15 metric tons of mercury are used annually in the United States for the production of thermostats, primarily for home heating and cooling applications. Of the 70 million thermostats in residential use today in the United States, it is estimated that 90% use mercury. Thermostat manufacturers estimate that 2 to 3 million thermostats are brought out of service each year. Most of these thermostats are replaced by the homeowner or contractor."

Three companies dominate the U.S. mercury-switch thermostat market - Honeywell, General Electric, and White-Rogers.

Source: U.S. Environmental Protection Agency, "Mercury Usage and Alternatives in the Electrical and Electronics Industries," EPA/600/SR-94/047, May 1994; http://www.nema.org.