a    2017
b    Refers to Seoul Special City.
c    2018
d    Data classified according to ISIC Rev. 4.
e    Estimate.
f    Calculated by the UN Statistics Division from national indices.
g    2016
h    Excluding water and waste management.
i    2014
j    Data refers to a 5-year period preceding the reference year.
k    2015
l    Refers to foreign citizens.
m    Data as at the end of December.
n    2009
o    Population aged 3 years and over.
p    Population aged 16 to 74 years.
q    Do not correspond exactly to Frascati Manual recommendations.
r    2004
s    Including nationals residing abroad and crew members.
t    Development Assistance Committee member (OECD).