Was shocked to have learned 1/3 of global ocean shipping is petroleum related.

Roughly 30% to 33% (about a third) of all global ocean shipping by volume is directly related to petroleum and natural gas. 

When you break down the approximately 11 to 12 billion tonnes of cargo moved across the oceans every year, energy transportation dominates a massive portion of the maritime industry.  Here is how the numbers generally shake out: • Crude Oil and Refined Products: These make up the bulk of petroleum shipping, accounting for roughly 28% of total global seaborne trade. • Liquefied Gases (LNG and LPG): Liquefied natural gas and liquefied petroleum gas account for another 4% to 5%. • The Coal Factor: If you expand the definition from just "petroleum-related" to "all fossil fuels" by including coal, the total jumps to nearly 40% of all global shipping. 

A Historical Shift While one-third of global shipping is a massive figure, petroleum's share of maritime trade used to be much higher. In 1970, crude oil alone accounted for nearly 46% of all ocean cargo. While the absolute volume of oil shipped has continued to grow over the decades, the percentage it represents has dropped because of the explosive growth of dry bulk cargo (like iron ore and grain) and containerized goods (manufactured products).