The student-to-teacher ratio in Korean elementary schools dropped below 20 to 1 for the first time last year, while the proportion of those aged 65 and over to the entire population rose to 10.7 percent, according to a report by Statistics Korea released Thursday.

The figures confirm the aging trend and low birthrate. The student-to-teacher ratio in elementary schools stood at 19.8 to 1, as the number of elementary schoolchildren fell 15.9 percent between 2000 and 2009 from 4.02 million to 3.47 million.

Yet Korea's entire population was 48.747 million last year, up 0.29 percent on-year, while the number of households increased 1.5 percent to 16.917 million.

The proportion of over-65s to the entire population reached 10.7 percent last year, up from 7.2 percent in 2000.

Statistics Korea predicts that the country will become an "aged society" by 2018, when the proportion of elderly people reaches 14.3 percent. Any proportion over 7 percent means a society is categorized as ageing, while a proportion over 14 percent means it is aged.  

Meanwhile, the number of unmarried Koreans increased as many young people did not want to get married while many elderly people were left to fend for themselves. Also, some 309,000 couples tied the knot last year, down from 327,000 the year before, while 127,000 couples split up, up from 117,000. All this led to the proportion of single-member households rising to 20.2 percent from 15.6 percent in 2000.