A single figure sets Venezuela apart from the rest of the world: 303 billion barrels of so-called proven oil reserves. But experts say the country's estimate is inherently problematic and far from proven — rooted in exaggerated, aging data from a corrupt government.

The number has long been touted by politicians and investors as an important measure of untapped energy potential, most recently by President Donald Trump's administration in detailing a sweeping deal for the U.S. to take control of some Venezuelan reserves.