For the years 1980 to 1989 the data sources are
EIA
and
IEA (imports/exports).
For the years 1990 to 1991 the data sources are
EIA
and
IEA (imports/exports).
For the year 1992 the data source is
IEA.
For the year 1993 the data sources are
EIA
and
IEA (imports/exports).
For the years 1994 to 1999 the data source is
IEA.
For the years 2000 to 2021 the data source is
Ember.