a quick quote that i think is great
Gambling is a multinational industry that is regulated locally. As a result, there are regional variations in the games that are available and the regulations that control them. Fruit machines in the United Kingdom, for example, are required by law to pay out a minimum percentage within a short period of time (Parke & Griffiths, 2001). Apparently this regulation came into effect because the bar owners responsible for these machines were worried about potential losses due to the volatility of games (Jonathan Parke, personal communication). According to U.S. patent #6,666,765 (http://www.uspto.gov/patft/index.html):
[British] fruit machines generally use a form of “adaptive logic” wherein coin-in and coin-out is monitored over time and wherein odds/payouts of the fruit machine are proactively adjusted to achieve a target win percentage. Examples of adaptive logic fruit-machines in Great Britain are GB 2 185 612 A and GB 2 087 618 A. In the United States, the casino game operated with a random number generator must, over all play of the casino game, provide a known player expected return (or house advantage) and the casino game cannot proactively monitor performance and correspondingly adjust play parameters.
As a result, some of the myths about slot machines in North America may in fact be true in the United Kingdom (Griffiths & Parke, 2003; Parke & Griffiths, 2001). Parke (personal communication), however, recently told us that adaptive logic machines are being phased out as the United Kingdom moves toward adopting North American standards in order to permit larger prizes.