The gap between the incomes of poor and wealthy citizens is larger in the United States than in any other industrialized country. Last year, for the first time in almost two decades, low unemployment and increases in the minimum wage helped boost the earnings of Americans at the bottom of the pay scale. But tax policies and the use of stock options as part of corporate executives' compensation packages are helping to divert a growing portion of the nation's wealth to the richest Americans and away from the poor and the middle class. If the current economic boom continues, unskilled workers and those at the low end of the compensation pool will continue to benefit, experts say. But the disparity in Americans' incomes is not likely to disappear.