The potential benefits of energy efficiency measures can be significant. The international Energy Agency considers energy efficiency as the world's "first fuel" and estimate the 2012 global investment market in energy efficiency at between 310 billon and 360 billon. A significant potential foe energy efficiency exists in emerging economies outside the OECD, with efficiency able to slash up to 90 bllion in global transport-related fuel costs by 2020 while reducing local air pollution. In maritime transport, key regulatory instruments addressing the nexus between energy, air pollution and carbon emission from shipping are the technical and operational measures mandated by IMO in 2011. The relavant requirement include the Energy Efficiency Design Index(EEDI) and the Ship ....(SEEMP). Inconsidering 22 potential ship efficiency measures and calculating their aggregated cost effectiveness and reduction potential, one study finds that, by 2020 the industry growing fleet could reduce annual co2 emission by 33% of the project annual total. Another study investigated 28 energy-saving options and esimated a reduction of co2 emission in shipping by 2030 of more than 50% . Other relavant measures include those relating to the IMO sulphur limits imposed on fuels used by ship, globally as well as in designated ECAs