Google co-founders Larry Page and Sergey Brin plan to sell 5 million shares apiece of their company stock, worth $5.5 billion combined at current prices.

The sales will occur periodically during the next five years and leave the two with 48 percent of the voting power among stockholders, down from roughly 59 percent now. But with Google Inc. CEO Eric Schmidt controlling nearly 10 percent voting power, the trio will still control the company.

According to regulatory documents filed Friday, Page and Brin will still own 47.7 million shares combined after the sales.

Shares fell $2.71, or 0.5 percent, to $547.30 in extended trading Friday.