Over many parts of the world, there is an increasing trend of rise in the percentage of casual employment.
I have heard the highest figure is in Norway, with Australia being second with 25% of the work being casual.
See, for example, an old American paper that touched on this subject, while examining the pathology of American ghettos. http://web.archive.org/web/20031118102645/http://homepage.mac.com/paytonc/repository/ghettoes.pdf