# Is this a valid or legitimate way of comparing countries on traits and characteristics?

Country A has 16 million inhabitants and 2.000 MW of solar panel generated power, also a GDP of $50.000 per capita Country B has 160 million inhabitants and 2 MW of solar panel generated power, also a GDP of$10.000 per capita

Would it be correct to say that country A has two thousand times as much solar power because:

• If country A was as populous as B, they would have 20.000 MW in solar power.

• But if country A was as poor as country A, they would have 4.000 MW solar power. So, after adjusting for differences in population and wealth, country A still has 2000 times the solar power that country B has?

Is it correct to adjust for differences in population and wealth in that manner, or not?

Follow up question: Is there a formal way, when comparing countries or groups, to adjust for differences in various traits (such as population size and GDP per capita?)

I have no idea whether there are formal rules, but you can emulate physical scientists and look at the units.

Dividing solar power by population is reasonable, as you get megawatts per capita. Those refer to real quantities.

However, you are dividing by GDP (in a roundabout fashion). The units of GDP are (currency unit)/(year). Since megawatts are a real quantity, and thus no currency value, the resulting ratio is (megawatts)(years)/(currency unit). This does not appear to correspond to anything.

You could try to fit a model that predicts solar capacity as a function of wealth and population, and the model calculations should implicitly correct the units.

• mWh (megawatt hours) per capita or mWh/dollars seem very clear, whereas the model will be subject to underlying assumptions. Apr 10 '19 at 14:29
• With currency in there, the measure depends on inflation. Apr 11 '19 at 10:52

There are various ratios that can be calculated relating energy production to economic variables or population. Generally they are neither correct nor incorrect: what should be asked is whether they are meaningful or useful for a particular purpose.

One commonly used ratio is energy intensity, the ratio of GDP to energy use. Broadly, a high ratio indicates that energy is being efficiently used in the economy. Another is energy consumption per capita, consumption here including all energy used in the economy, not just that used by end users.

Possibly I am missing something, but I cannot see that a calculation as in your question relating an energy variable to both GDP and population is especially useful.

It's also important to note that electrical energy and electric power are distinct concepts. Electric power can be measured as you indicate in megawatts (MW). Electrical energy also requires a time dimension so might be measured in megawatt hours (MWh). If a power source were to operate uniformly at all times then the energy in MWh it generated annually would simply be its power in MW multiplied by the number of hours in a year. But many sources do not operate uniformly, eg power stations may be shut down for maintenance or run at less than full capacity due to limited supplies of fuel inputs. In the case of solar power, power output is limited to when the sun is shining. So, comparing countries A and B, the energy generated from solar depends not only on their respective installed power but also on their respective hours of sunshine, which could be quite different.