Who the most loyal and productive at work : Married employee or Unmarried employee, why?

Married for sure as they already have motivation to support their families

both married and none married are the same when it comes to work, if the company's priority is not being dealt with all as equal, then none of the categories will be interested to continue and will consider their present work as a bridge.

the alternative question should be, can a company accommodate a policy that works for both married and none married alike?

married employee since they know that they will have to work extra hard because they already have a family

Married employees...............................................................

It depend on the person tempertuer

some times it is good  and other not

Even an unmarried person can be supporting his parents and siblings . So a person with lots of financial responsibilities will be productive at work. Older people do not change jobs often like youngsters do. Also a non localite who has to support himself ( with rent and other expenses ) would be a good worker. The main lookout for the hr dept is the candidate really wants the job and not mere ly using the job a stop gap. 

When we come out to take any responsibility then our marital status should not be the hindrance in fulfilling all the duties. I worked as teacher for14 years but I never quit because of my domestic commitments. When your profession becomes your passion then doesn't matter married or unmarried :)

There is no stable ration in such comparison. Loyalty and productivity depend on the person himself if he or she is already loyal regardless the status. You may find many loyal unmarried and married people. And same for productivity.

In order to have a clear answer we need the results of some researches about such factors !

The married one because they have responsibilities of their families to support them and these responsibilities shows his/her loyalty with work.

obviously married employee because they have to support their families.  

If you link loyalty and productivity with responsibilities you might think yes married people might seem to have dependents and might care more, however this not accurate, loyalty and productivity of an employee can't be measured by marital status, commitment to work is based on what an employee is ready to give or to give up for the company, married employees do look for a more "stable" work life however this does not include all married employees, and single can also show a high desire of stability and show much more productivity than married employees

So the most loyal and productive employees are the ones who actually show care and work hard regardless marriage