How to determine the unemployment rate in a country?

Unemployment is determined by the ratio of the number of unemployed to the total number of the economically active population.
Both indicators are measured in terms of the number of people. Unemployed means people who are officially registered at the employment center. The economically active population is precisely divided into employed and unemployed. General attribution to the economically active population is characterized by the ability to perform work in principle, that is, one must be over 16 years old, want to work, be employed or is in search of work and be ready to start it at any time.