None of the Waltons have signed The Giving Pledge, an initiative by Gates and Buffett to get the world’s billionaires to commit to giving away a majority of their wealth during their lifetime, or at their death. The top four givers on the Forbes list – Buffett, Gates, Bloomberg, and Ellison – have all signed the pledge. Only the Waltons and the Koch brothers have not.

Since 2000, The Chronicle of Philanthropy has compiled an annual list of the top 50 American contributors to charitable organizations. None of the Walmart heirs discussed here has ever appeared on that list.

We knew the hugely wealthy Walton family was greedy and cheap when it came to other people. You only have to look at Walmart's labor practices and global supply chain to know that. But it's shocking to see just how ungenerous they are when compared with their peers among America's wealthiest billionaires:This analysis, by Making Change at Walmart, only includes giving to the private charitable foundations associated with the individuals and families on the list. That means that direct giving without going through the foundation isn't included. But the Waltons aren't giving a lot to their own family foundation—in fact, they're using it to get out of future estate taxes —so it doesn't seem likely that they're secretly giving huge amounts of money to charities directly while not giving to their foundation. Additionally: Meanwhile, the workers in their stores are paid so little that many are forced to rely on food stamps and other government assistance to get by. "Parasites" doesn't seem like too strong a term to describe the Waltons.