By BILL GATES We can learn a lot about improving the 21st-
century world from an icon of the industrial era: the steam
engine. Harnessing steam power required many innovations, as
William Rosen chronicles in the book "The Most Powerful Idea in
the World." Among the most important were a new way to measure
the energy output of engines and a micrometer dubbed the "Lord
Chancellor" that could gauge tiny distances. Such measuring
tools, Mr. Rosen writes, allowed inventors to see if their
incremental design changes led to the improvements—such as
higher power and less coal consumption—needed to build better
engines. There's a larger lesson here: Without feedback from
precise measurement, Mr. Rosen writes, invention is "doomed to
be rare and erratic." With it, invention becomes "commonplace."
In the past year, I have been struck by how important
measurement is to improving the human condition. You can achieve
incredible progress if you set a clear goal and find a measure
that will drive progress toward that goal—in