Despite an early start in Great Britain with the Factory Acts of 1833, legislation has often appeared too late to deal with critical problems and is often difficult to enforce, especially in relation to the threat presented by exposure to toxics. The effect of these is often difficult to prove in a conclusive way. Many employees bringing compensation claims have found it hard to show employer liability. Of the half million people in the United States severely disabled as a result of occupational disease, fewer than 5 percent have received formal compensation.