Brazilian-born Facebook co-founder Eduardo Saverin, 30, traded in his American citizenship last September to take up residence in Singapore, a move that will cut his taxes when Facebook IPOs on Friday.

He is estimated to own about 4% or 5% of Facebook.

The company was valued at $77 billion-$96 billion ahead of the IPO although, according to Bloomberg, its roadshow is producing less institutional demand for the stock than expected since Facebook said last week that advertising revenues weren't keeping pace with user growth and may not reach its rosier forecasts.

It's supposed to go out at $28-$35 a share and sell 337.4 million shares, 180 million put up by Facebook itself. The rest of the shares are coming from CEO Mark Zuckerberg and selling shareholders like Accel Partners, Goldman Sachs and Digital Sky Technologies.

Saverin moved to the US in 1992 and became a US citizen in 1998.

A spokesman said, "Eduardo recently found it to be more practical to become a resident of Singapore since he plans to live there for an indefinite period of time. He has invested in Asian, US and European companies. He also plans to invest in Brazilian and global companies that have strong interests in entering the Asian markets. Accordingly, it made the most sense for him to use Singapore as a home base."

Singapore doesn't have a capital gains tax.