Salesforce.com founder and chief executive Marc Benioff has been aggressively reducing his equity stake in the company over the past two years, selling as many as 20,000 shares per day in hundreds of individual transactions, according to Securities and Exchange Commission records.

Benioff held 28.1 million shares of the hosted software maker's common stock as of December 2004, shortly before the sell off began. As of Monday, the flamboyant CEO's stake was down to 16.3 million shares, a reduction of 42%.

Benioff now holds roughly 14% of Salesforce's outstanding stock, compared with about 25% when he began selling.

Benioff is selling the stock under what's known as a 10b5-1 plan. Such plans allow corporate executives to specify in advance a preset number of shares to be sold off regularly over a specific time period.

The idea is that their trading won't be influenced by their insider's knowledge of company activity.

A spokeswoman for Salesforce said Monday that Benioff's sell-off represents nothing more than prudent financial planning. "He's completely transparent about this," said the spokeswoman. "It helps him diversify for personal, financial reasons."

Benioff has sold off Salesforce stock under three increasingly aggressive 10b5-1 plans starting in February 2005, SEC records show.

The first plan allowed him to sell up to 2.4 million shares at a rate of 10,000 per day. Under the second, he could sell up to 3.9 million shares in increments of 20,000 per day. The third plan, which started in August 2006 and ends next month, allows him to sell up to 5 million shares in Salesforce at 20,000 shares per day.

He's been doing just that. SEC records indicate that Benioff has sold 20,000 shares in Salesforce on virtually every trading day over the past several months.

So where does Benioff now stand in terms of other software moguls and their corporate stakes? About in the middle. Microsoft chairman Bill Gates has reduced his holdings in his company to 9.5% of outstanding stock as he transitions to full-time philanthropy.

On the other hand, Oracle CEO Larry Ellison still retains 23.8% of his company's stock.

Salesforce's stock trades on the New York Stock Exchange under the symbol CRM. It was poised to open Wednesday at $38.86 per share. The stock is up 7.7% on the year.