The 2010 guidelines for monitoring the worldwide
average sulphur content of fuel oils supplied for use
on board ships (IMO, 2010, annex I) provide for the
calculation of a rolling average of the sulphur content
for a three-year period. The rolling average based on
the average sulphur contents calculated for 2011,
2012, and 2013 is 2.53 per cent for residual fuel and
0.14 per cent