It’s not broken down by white collar/blue collar. My union represents everyone from the receptionist to the attorneys, but does nto represent anyone in management. The cummnity of interest needed to establish an approprate bargaining unit includes several factors such as whether they: perform similar types of work, have regular work contact, are subject to similar working conditions, have similar wage and benefit packages, are subject to common supervision, and the extent and form of organization, either with that employer or within that industry.
Supervisors and non-supervisors cannot be in the same unit, although there may be a unit of supervisors, as long as they are not management. Management is the level of people whose main tasks are organizational–they run the place, but are not directly or are only rarely or incidentally involved with the production/work product and or services of the organization.
A whole other concept is exempt and non-exempt. This applies the coverage under the Fair Labor Standards Acts–the law that brings us minimum wage and outlaws child labor. If you are covered by the FLSA (non-exempt), you must be paid overtime if you work over 40 hours a week. If you are not covered (exempt) you cannot be paid an hourly wage, non may your employer do anything that treats you as an hourly wage earner, therefore, no overtime (government employees can earn compensatory time). an employer can’t just declare a position exempt, it must meet certain criteria–in general, executive, administrative, professional, all of which include the concept that the person is more conconcerned with the running of the business than the product/service of the business.
A union contract (often called a collective bargaining agreement or CBA) cannot make someone exempt or non-exempt from the FLSA, although management often tries to use it to get a specific position out of the bargaining unit. A smart union rep will always look at the specific duties of the position to see if it fits a exempt category. If it does, it is not appropriate for ti to be in the bargaining unit.
The method of organizing one department at a time (or one retail store of a chain, or one nursing home of a chain, etc) is sometimes called retailing, and sometimes beach-heading. It established an example of a union within the business, and will therefore make it easier (if it is a good union and helps its members to gain better wages, benefits and workign conditions) to organize additional units (either as separate units with a wholely separate contract, or more likely, by accreating the new unit into the established unit and negotiating any provisions specific to the new unit into the existing contract). Obviously, going after the whole industry at one time (and under one contract with local side agreements) is called the going wholesale, and was much used in the early days of labor unions. Among some union activists, the idea of wholesale campaigns are again gaining popularity. Because so many companies (and therefore bosses) are national, and even international, unions may need to also become international in order to equalize the employment relationship and so promote reasoned capitalism.