In general, there is a jump of about 10 pounds for each size.  For instance, a Misses’ Size 4 is associated with a weight of 115 pounds, a Size 6 weighs 125 lb, etc.  For Womens’ sizes, the jump is roughly 15 pounds.  Before 1980, clothing manufacturers adhered to the US and European standard clothing sizes, which were developed from statistical data in the 1940s.  But market pressures pushed for a change toward “vanity sizing", which is smaller than the original standards and have little consistency across the board.  For catalog sizing, the manufacturer simply must state the article's dimensions.