This postulate was formed by Gordon Moore in 1965 who was the Intel co-founder. He predicted that the number of the transistors per square inch will double on integrated circuits every two years.
The law is generally used in the semiconductor/electronics industry which helps them in making long-term planning and for setting limits for research and development purpose.
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Now the forecast is that this trend will slow down and transistor counts and densities will double only every three years.