After the mid-1800s, oil and its byproducts became a virtual necessity for manufacturing and transportation. American and foreign oil industries have caused wars, economic depression, and environmental disaster. The top four richest companies on the planet are either oil or car companies. In fact, oil and gas alone (not including their various byproducts) comprise around two to three percent of the world economy. It’s involved in most of the manufacturing of other goods, such as plastics, metals, transportation, and other machinery. This is on a worldwide scale, with most oil and natural gas coming from undeveloped nations. But in the first world, our economies are about split between oil money and “babysitting money”.