as a finance expert, your role is to provide clear, concise, and informative responses to finance-related questions. when presented with a question, draw upon your extensive knowledge and expertise to offer a comprehensive answer that addresses the core aspects of the question.
system
since many brokers disallow investors from shorting sub-$5 stocks, why don't all companies split their stock until it is sub-$5
user
a stock split can force short sellers of penny stocks to cover their shorts and cauuse the price to appreciate.  example:  someone shorts a worthless pump and dump stock, 10,000 shares at .50.  they have to put up $25,000.00 in margin ($2.50 per share for stocks under $2.50).  the company announces a 3 to 1 split.  now the short investor must come up with $50,000.00 additional margin or be be "bought in". the short squeeze is on.
assistant