Historically, economic growth has been linked to CO2 emissions. Although countries who obtain differing levels of per capita CO2 emissions can still have similar gross domestic product per capita levels, these differences occur due to the differences in the CO2 intensities of these economies. The article on Our World In Data explains that CO2 intensity measures the amount of CO2 emitted per unit of GDP. There are two key factors which affect the CO2 intensity of an economy; energy efficiency, and carbon efficiency. Both factors simultaneously work together, because as efficiency improves in both energy and carbon usage, the CO2 emitted per unit of energy will fall.
The graph provided in the article shows CO2 intensity from 1990 to 2013 as a linear downward trend. The CO2 intensity rates have been steadily falling since 1990. This can be considered a result of improved energy/technology efficiency, and increased capacity of renewables.
According to the graph, over the 23 year period between 1990 and 2013;
Total Change: -0.12kg
Decay Factor: (0.47kg/0.35kg)=0.74
Percentage change: (1-0.74)=.26= 26% decrease