According to the text, in recent years the ratio of earnings of the typical U.S. college graduate to the earnings of the typical high school graduate without additional education has: A. Increased as the demand for skilled labor has decreased relative to the demand for unskilled labor. B. Decreased as the demand for skilled labor has increased relative to the demand for unskilled labor. C. Decreased as the demand for skilled labor has decreased relative to the demand for unskilled labor. D. Increased as the demand for skilled labor has increased relative to the demand for unskilled labor.