This article discusses how important it is for countries to secure their energy supply. The researchers developed a method to measure how secure a country's energy supply is by looking at how much energy a country depends on imports and how diverse its sources of energy are. They applied this method to Korea from 1991 to 2018 and found that even if a country has many sources of energy, if it relies heavily on imports, its energy supply may not be secure. This shows that it's crucial for countries to balance energy diversity with minimizing dependence on energy imports to ensure a secure energy supply.