Estimates of the total amount of oil in the world have steadily increased as technological progress in extracting oil from remote sources has led to more efficient production.
(Estimates of the total amount of oil in the world; have steadily increased; as technological progress in extracting oil from remote sources) (Estimates of the total amount of oil in the world; has led; to more efficient production)
Estimates of the total amount of oil in the world Estimates of the total amount of oil in the world
have steadily increased has led
as technological progress in extracting oil from remote sources
to more efficient production