What I have found over the years is that the older workers are far more efficient than the younger ones...Employers have standards that have to be met...If an employee can no longer meet those standards, there are always provisions in the contracts to address that...
When I have seen older employees replaced by younger employees it is not for smarter or faster...It is for cheaper wages and benefits...Seniority is good...It protects the workers as long as they are still able to do the job required of them...The teacher's unions are a different creature...
Another way seniority is good is after you have worked your job for a while, seniority prevents a buddy of the boss from moving up instead of you while you are just as qualified to do the job...Certainly doesn't hurt the company and makes for happy workers...
I referred to “last one hired, first one fired” unions pull when budgets are cut as a result of poor negotiations — or in the case of Wisconsin, when the public union bosses/rep/negotiator/whatever you think is the PC equivalent refuses to negotiate.
Age has nothing to do with that.