Beyond the legal aspect, there are good reasons not to discriminate by age.
Beyond avoiding an age discrimination charge, there can be significant advantages to hiring older workers. Including them in your candidate mix does not just prevent the negative of a lawsuit; it can provide positives as well.
The default position in such situations is to take caution and warn against potential negative outcomes (lawsuits, fines, penalties, etc.) that come from discriminatory behavior. I would respectfully suggest an additional approach to include in your company philosophy.
They easily adapt.
For years I have said that mature employees offer more bang for the buck than what's often considered a traditional age-appropriate hire. I mean that in an economic way. Based on salary and value, mature candidates are an undervalued stock. They are more experienced and, because of that, adjust to a new job quicker. Why? Because they've done it many times before.
Managers who have hired new people know it can take months before an employee becomes productive. Cutting that time in half is a huge advantage to a company's efficiency. Moreover, in a shorter amount of time, you can get a highly experienced and skilled employee who will adapt to change for the same salary as someone whose career is still formative. Despite the impression that mature workers can't learn new things, I would propose that, if a 20-to-30-year career teaches someone anything, it's how to adapt to change.
They're in it for the long run.
There is another important benefit to the mature candidate: less likelihood of employee turnover. In my experience, the mature employee is more interested in the job content, co-worker dynamic and convenience of the commute than with salary or career track. Since they are willing to make career advancement secondary, they are often more concerned about their existing position than what happens tomorrow. For an employer, that can be a good thing. Not everyone you hire should want to be a VP. Having too many chiefs is not a good organizational dynamic model.
Pay a fair salary, give a daily challenge, surround them with quality people and they are content. Many people who have been in the same career for decades don't ask where the job will lead them, because they have already established their careers. The next step they're looking forward to may not be a promotion, but retirement. As a manager, would you rather have an employee who will give you a solid five years of work or an employee who may move on in three years for another job because they weren't promoted?
Caution: Don't overhire.
When considering a mature employee, there is a large caveat to consider. There is a significant difference between an employee who is taking a job at a level consistent with their experience and one who is taking a step back. Hiring someone overqualified for a position will not be beneficial to either party for two reasons:
1. A manager moving to an individual contributor job is not just taking a step back; they are actually moving into a different role. Managing is a separate skill set from doing. Be careful not to make assumptions about competence based on a false premise. Someone who has been an accounting manager may not be the best cost accountant.
2. You must reinforce that the person is being hired to do a specific job and not to mentor young co-workers. It is human nature for someone in their 50s or 60s to want to mentor someone in their 30s. I call that the Old Philosopher Syndrome. When a manager in their 30s is managing a person in their 50s, it needs to be clear that the relationship is boss to employee, not Daniel-san to Mr. Miyagi.
After careful consideration and weighing all the options, I believe firmly in hiring mature employees. In an increasingly competitive candidate marketplace, these hires can bring great expertise, knowledge and value to the company at hand.