GDP: US CO2 Emissions - IPAT-S Tutorial

Avoiding the GDP Variable - Rewriting the Basic Equation

The next step is to specify the GDP. However, it is not necessary to do this explicitly. The question asks for how population and GDP per capita might drive total emissions. So, instead of GDP, use population as a driver, modified by GDP per capita. This gives a relationship:

Pop >> GDPperCapita -> GDP >> EmissionIntensity -> Emissions

Pop >> GDPperCapita -> GDP >> EmissionIntensity -> Emissions

or, better yet,

Pop >> GDPperCapita * EmissionIntensity -> Emissions

which omits GDP entirely. In this case, the script can be re-written

base year 2002
scenario year 2012

summvar Emissions
ratio EmissionIntensity

Emissions.by = 100
EmissionIntensity = incr[-18%]

::   Pop >> GDPperCap * EmissionIntensity -> Emissions