If you read my earlier article on why I wished UPS were public, you'd know that, unlike most privately held companies, UPS is already fairly widely held. That's quite a substantial number, considering the program is completely voluntary, and employees must work for the company for at least one year to become eligible. The interesting thing is that, again unlike that of most private companies, UPS stock is not illiquid.
Employees can purchase shares from and sell shares to the company at the set price.
The main difference, of course, is that the company, not a public market, determines what the shares are worth. With the IPO, UPS will now get a market valuation. Current employee-shareowners will get Class A common stock, and a new class of B shares will be offered to the public. Essentially, Class B shares will cost the same as Class A shares, but Class B shareowners will have only one-tenth the voting power. Class A shares can be converted to Class B shares upon transfer or sale, giving employee-shareowners the ability to sell their shares to anyone, not just to the company.