The 2011 Update is an excellent way to keep users abreast of global changes. A supplement containing 25 to 40 replacement maps and a new cumulative index, the Update allows those who have recently purchased a complete edition of Maps On File to keep the collection as current as possible. The 2011 Update is an indispensable tool for bringing older editions up to date but does not need to be ordered if the 2011 Edition is purchased.