Decline in North Korean defectors

From official sources, we see that North Koreans who flee their country has almost always been a steady increase since late 1990s, until recently years.
From 2012, the number remains low compared to previous years, with around 1500 defectors per year. And why 2012? It was the year when Kim Jong Un came into power.

The reason behind the decrease may not be that people have enjoyed higher quality of life under KIM Jong Un's era and thus abandoning the will to defect, but rather that they face higher hurdles, such as wires with high voltages, harder to escape border guards' eyes, or fierce punishment can be imagined.

Those who decide to defect usually choose wintertime, when Tuman river is frozen so that they can walk across, stepping into Chinese border.