The United States Labor Department says that a new study shows that between 3.5 and 6.5 percent of all the wage and salary workers in California and New York are paid less than the minimum wage. The study, which examined work force data for the two states, found that more than 300,000 workers in each state suffered minimum-wage violations each month. Labor Department officials said that even if one assumed a violation rate half that nationwide, that would mean more than two million workers across the nation were paid less than the federal or state minimum wage.