We run a job board where people create resumes and apply to job offerings.
For each of their previous workplaces, we require them, amongst other things, to enter the city they worked in. As you might have guessed, the city field is open (i.e. a normal text field)
We decided it's high time to close that field and offer a combo box. When looking at the various values people have entered in the city field, we found that a lot of users entered more info than was required (e.g. city+district, the company's full address,
or even all the cities that the company has offices in).
This led me to believe that whenever people have open text fields, they tend to provide more info than required, or even more info that would be sensible to include (you usually don't write full addresses of previous workplaces in your resume)
Is there any research on this subject? I'm interested to know how much people tend to abuse open fields, and when to close fields for the sole reason of suggesting people what info should they include.
As a side question, how to mitigate user's expectations when closing such fields?
(i.e. some of them might expect the 'city' field to be left open and may find annoying when websites tinker with their info)