I've been involved in hiring employees for 20 years in the western US and while there has always been a good percent of applicants that bounce between jobs I do feel it has become more common. We have certain positions that we just plan on being fairly short term, especially positions that attract college students, and in those cases we have developed significant training documentation which has made turnover much less painful.
The best way we have found to develop that training documentation is to have the new employee do it as they are trained. Because the new employee doesn't generally have much institutional knowledge they are best positioned to document tasks from the perspective of the next employee who will lack that knowledge too. It has also shortened the training process because instead of revisiting instructions in week two when the employee forgets how to do a task, they just refer to their notes from week one.
Good luck!