Date	Event	Description
27 July 2016	Amended	Brief Economic Commentary added.
30 October 2014	Amended	Minor text amendment
23 April 2013	New search has been performed	Review text updated
23 April 2013	New citation required but conclusions have not changed	New search identified one additional study for inclusion. Conclusions unchanged.
13 October 2008	Amended	Converted to new review format.
12 July 2000	New citation required and conclusions have changed	Substantive amendment