If you cannot measure it, you cannot improve it.
As of the writing of this book (December 2014), there are 28 countries that either currently produce electricity from geothermal energy or used to do so. Four countries (Argentina, Democratic Republic of the Congo, Greece, and Zambia) have shut down very small power plants.
The growth of geothermal power worldwide is shown in a semilog plot in Figure A.1. It can be seen that the geothermal industry has experienced several different periods of development. Until World War II, Italy was the only country with commercial geothermal power plants. From 1930 to 1944, the average annual growth was about 14%. ...