Want to get a sense of just how bad the News of the World phone hacking scandal has been for Rupert Murdoch? Look no further than News Corp market value.

The company has lost $7 billion in market value over the last four trading days, reports Bloomberg.

The company "tumbled 4.6 percent to A$15.19 in Sydney today. The stock lost $1.27, or 7.6 percent, to $15.48 in Nasdaq Stock Market trading yesterday, the biggest drop since April 2009. It was the fourth straight decline in the company’s closing price, cutting its market value by 15 percent to $41.2 billion. "

At 538.com Nate Silver notes a big chunk of that is from yesterday alone [below].

The question remains: How much money does News Corp have to lose before Rupert Murdoch chooses to lose top lieutenants instead?