If a firm declares a 20:1 stock split, and the pre-split price was $500, then we might expect the post-split price to be $25. However, it often turns out that the post-split price will be higher than $25. This higher price could be due to signaling effects--investors believe that management split the stock because they think the firm is going to do better in the future. The higher price could also be because investors like lower-priced shares.