The proportion of those in their prime working age out of the total economically active population dropped to its lowest point in the first quarter this year, Statistics Korea data showed Saturday.

The number of those in the 25-49 year age group was 19.241 million in the period, dropping 0.4 percent from the same quarter last year. That accounted for 44.1 percent of total economically active people, which is 43.633 million. This is the lowest rate since data was first collected in the third quarter of 1999.

The ratio of prime-aged workers continued to decline after reaching a peak at 54.4 percent in 2001, due to a low birthrate and aging society.

The employment rate among prime-aged workers has also continued to fall. Out of 25.915 million people employed in the first quarter this year, 55.9 percent were aged between 25 and 49. This is a plunge from 67.9 percent in the first quarter of 2000 and a drop from 59.3 percent in the second quarter of 2012.

Those aged between 25 and 49 are considered to show the highest productivity and consumption power, meaning a drop in the number of this group leads to a weaker growth potential.