Google reports fourth-quarter profit

* Q4 revenue rose 18 percent to $5.7 billion

* Q4 GAAP earnings per share $1.21

* Says announced that it is planning to offer employees a voluntary,

one-for-one stock option exchange

* Q4 traffic acquisition costs $1.48 billion

* Says program intended to create more incentives for employees to remain at

GOOGLE (GOOG.NQ)/p>

* Reuters Estimates Q4 earnings per share view $4.95, revenue view $5,641.91

million

* Says expect to take modification charge estimated to be $460 million over the

vesting periods of the new options

* Says expect to continue to make significant capital expenditures

* Says continue to invest in Google's core search and ads business

* Says on worldwide basis employed 20,222 full-time employees as of December 31

up from 20,123 full-time employees as of September 30

* Says will continue to invest in strategic growth areas such as display,

Mobile, and enterprise