Demographers determine the age structure of a given population by dividing it into five-year age-groups and arranging them chronologically in a pyramidlike structure that "bulges" or recedes in relation to the number of persons in a given age cohort. Many poor, developing countries have a broad base and steadily tapering higher levels, which reflects a large number of births and young children but much smaller age cohorts in later years as a result of relatively short life expectancies. North Korea does not entirely fit this pattern; data reveal a "bulge" in the lower ranges of adulthood. In 1991 life expectancy at birth was approximately 66 years for males, almost 73 for females.
It is likely that annual population growth rates will increase, as well as difficulties in employing the many young men and women entering the labor force in a socialist economy already suffering from stagnant growth. Eberstadt and Banister project that the population will stabilize (that is, cease to grow) at 34 million persons in 2045 and will then experience a gradual decline. By comparison, South Korea's population is expected to stabilize at 52.6 million people in 2023.