Then there is David Novak, executive chairman of YUM Brands (YUM.N), the conglomerate that runs Taco Bell, Pizza Hut, and KFC outlets. Novak’s total retirement holdings, including deferred compensation, are worth $234 million – more than any other Fortune 500 chief executive. Novak tops the list of Fortune 500 CEOs with the largest retirement nest eggs, according to a study from two progressive think tanks – the Center for Effective Government and the Institute for Policy Studies.