been falling for 150 years, declining even faster in the last two decades. In 1870 it took 4 kilograms of stuff to generate one unit of the U.S.’s GDP. In 1930 it took only one kilogram. Recently the value of GDP per kilogram of inputs rose from $1.64 in 1977 to $3.58 in 2000—a doubling of dematerialization in 23 years.
