Junior is about to head off to college and doesn't know which major to pick. Naturally he'll try to find something that he likes. But it's also important to learn a skill that will help him find employment after he graduates. The first question he'll need to ask is whether there will be demand in five, ten and twenty years for the skills that he'll learn. For instance, personal computers have decreased the demand for secretaries and bookkeepers.
More demand means a more secure future.
That doesn't mean that Junior should avoid every field that has a small need for people. It's possible that no one is entering a specific field. In that case he might do fine. The trick is to find a career where the demand for employees is greater than the number of trained people available. The benefits of careful career selection will follow Junior for years.