For that indicator, Medina and Schneider (2018) provides data for South Korea from 1991 to 2015. The average value for South Korea during that period was 25.7 percent with a minumum of 19.83 percent in 2015 and a maximum of 30.04 percent in 1998.
See the global rankings for that indicator or
use the country comparator to compare trends over time.
Definition: The shadow economy as percent of total annual GDP. Detailed methodology of the estimations can be obtained from the following International Monetary Fund working paper by Leandro Medina and Friedrich Schneider (2018): Shadow Economies Around the World: What Did We Learn Over the Last 20 Years?