3.1.2. Energy Import Dependence

Energy import dependence is one of the most used metrics for assessing energy supply security. It describes the percentage of total energy imports over the total energy supply of a country. Fossil fuels, such as oil, coal, gas, and uranium, are the energy sources that this index evaluates across different regions and countries [6,19]. It is expressed as follows:

$$D\_2(\%) = \frac{EI\_T}{ES\_T} \times 100(\%) = \frac{\sum\_{i=1}^{N} EI\_i}{\sum\_{i=1}^{N} ES\_i} \times 100(\%)\tag{2}$$

where *D*<sup>2</sup> is the energy import dependence, and *EST* and *ESi* represent the total amounts of all types of primary energy supply and the *i*th primary energy supply, respectively. In this term, *EIT* and *EST* use the same monetary or physical unit.
