Iran, Saudi Arabia square up across world&rsquo

There are several reasons why escalating tensions between Iran and Saudi Arabia make markets nervous. One of them is that they sit on either side of the Persian Gulf, the world’s biggest concentration of oil tankers.

At the mouth of the Persian Gulf is the Strait of Hormuz, the world’s most important choke point for oil shipments, with about 17 million barrels of crude passing through daily, according to the US Energy Information Administration. Oil prices jumped more than 3 percent.