Trade unions : good ? evil ? necessary ?

As a Labour Relations consultant, I hear different opinions about trade unions on a daily basis.

The views I hear the most are:

- Unions are necessary to give some power and resources to the employees when they have conflict with management

- Unions are out of date. With the labour codes and human rights being reinforced over the years, there is no longer a need for unions.

- Unions reduce productivity by raising wages and imposing restrictions in management's methods.

What is your idea about trade unions and their role in improving the workers' condition?