Bill walks into a bar, orders a drink, and begins playing pool. Several minutes later, one of the bar's regulars insults Bill, who punches the man and thus starts a fistfight. This scenario depicts an example of .

The changes to agriculture in the united states since 1900 is that increased mechanization has increased food production, thereby increasing the need for labor. there has been an increased need for higher speeds of food production due the fact that the population in the united states continues to rise.