1."Whether national elections are free and fair";
2."The security of voters";
3."The influence of foreign powers on government";
4."The capability of the civil servants to implement policies".

the democracy index is a weighted average based on the answers of 60 questions...The questions are distributed in the five categories: electoral process and pluralism, civil liberties, functioning of government, political participation, and political culture.
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there are a few questions considered so important that a low score on them yields a penalty on the total score sum for their respective categories, namely:

"Whether national elections are free and fair";
"The security of voters";
"The influence of foreign powers on government";
"The capability of the civil servants to implement policies".