Why do oil reserves keep growing every year despite constant predictions that the world will run out of oil in the next 30 years?

Why do oil reserves keep growing every year despite constant predictions that the world will run out of oil in the next 30 years? In the 1970s former U.S. President Jimmy Carter declared that the world's confirmed oil reserved would be consumed in a decade. World oil reserves then amounted to 550 billion barrels. In 1990, reserves exceeded one trillion barrels and now has reached 1.7 trillion barrels. At the current rate, it's expected to exceed 2 trillion barrels in the 2020s. Analysts point to U.S. production ofshale gas technology, which has made previously inaccessible supplies of oil available for extraction, as the reason for a large boost in world oil reserves.