In 2011, oil tankers spilt less oil than ever before since records began, according to the excellent International Tanker Owners Pollution Federation. There were only four medium sized spills and one large one, for a total of about 1,000 tonnes. Better ships (with double hulls), better equipment (such as GPS), better communications and better training have all helped drive tanker spills down. In contrast, other types of ships (like container ships and cruise ships) are spilling more oil and other pollutants, such as 100 tonnes of styrene monomer from the Haldoz in Spain.
ITOPF publishes a very useful set of Technical Information Papers on oil and chemical spill response, and on managing the compensation claims that follow.