Human errors exist because to err is human. Some are costly and some inconsequential. The definition of human error varies somewhat depending on the source, but all contain the statement that an error was committed involving a human who failed to achieve a desired outcome. The error may occur in either the execution or the planning stages. Plans can be improperly made but implemented correctly; it could be properly made but poorly implemented; and in the worst case, it could be both poorly made and poorly implemented . Although the prevention of human error has been the subject of numerous articles and books, it persists today and the rate of commission is even increasing. In fact, one study suggests that the contribution from human errors has increased from a low of approximately 20 percent during the decade of the 1960s to more than 80 percent in the decade of the 1990s. This is more than a 400 percent increase. This increase is attributable to an upward trend in the sophistication of components and to mistakes that can and often occur due to creations caused by the designs of designers, situations exacerbated by managers, and decision makers .