The reason is that they are highly levered with many small short term trades. >dealbook.nytimes.com/2014/07/21/senate-inquiry-faults-hedge-funds-tax-strategy/https://dealbook.nytimes.com/2014/07/21/senate-inquiry-fault... “Jul 21, 2014 Within these complicated financial structures, Renaissance Technologies was able to borrow as much as $17 for every $1 in the account.”