What keeps business owners up at night? The fear of losing customers.

Companies spend billions to create the next big thing and then billions more on advertising to persuade consumers to buy it.

Do labor unions have that same worry?

A new poll by National Employee Freedom Week, a coalition of 99 nonprofit organizations in 42 states, suggests many do not. The poll asked members of union households if they knew they could opt out of union membership without losing their job or incurring any penalty.

Nationwide, two out of every five didn't know they had this option.

Imagine if two-fifths of Wal-Mart shoppers didn't know they could shop at Target, Amazon or another competitor.

When word got out, there would be a public outcry that Wal-Mart had acted like a monopoly. Its competitors would mount advertising campaigns to inform consumers about their alternatives. State attorneys general would launch investigations.

Wal-Mart executives, meanwhile, would hold emergency meetings on how to keep their customers from defecting to competitors. They would likely cut prices and boost quality to try and keep customers from bolting.

There is no comparable outcry, though, for the nearly 6 million union members nationwide who don't know they have a choice.

Many union employees do want to opt out of union membership. Another NEFW survey found over a quarter of those in union households would leave their union if they could without getting penalized for it.

Astonishingly, they already can but don't know it. In right-to-work states, workers can opt out entirely of union membership and all union dues.

In non-right-to-work states, employees can resign from union membership, become agency fee payers and receive a rebate for the union's political spending. Union members with religious objections to their union's activities - like the unions that gave hundreds of thousands in dues to America's largest abortion provider - can have their entire dues redirected to a non-objectionable charity instead.

Workers' ignorance of their legal rights has inflated organized labor's balance sheets. Polls also show most union members think they receive too little value for the dues they pay. Many pay up anyway because they think they have no choice. No other private organization in the country can collect literally billions from individuals who don't know they can say no.

A major reason union members don't know they can leave is their employers automatically deduct union dues from their paychecks. How do you stop something that looks as automatic as your Social Security deductions?

This perception enables union officers to run their unions according to their own preferences instead of catering to their members' desires.

For example, most major unions spend their members' dues heavily on political activities. Last year the AFL-CIO national headquarters spent a fifth of its $200 million budget on politics and lobbying. Almost all that money went to support left-wing politicians and causes.

However, many union members are conservatives or independents. Even many left-leaning members don't want to give their money to politicians. Polls also show three-fifths of union members consider their union's political spending wasteful.

Union officers do it anyway. They feel much less pressure to serve their customers than Wal-Mart and other businesses do. When your customers don't know they can leave, why cater to their needs?

That is, unless the groups participating in National Employee Freedom Week help the two-fifths of currently uninformed union members understand they have the ability to opt out of union membership.

-Victor Joecks is executive director of National Employee Freedom Week. James Sherk is a research fellow in labor economics at The Heritage Foundation