According to the SketchUp help website, I should be able to save a sketch up file made in 2016 as a 2014 file. However, every time I try to save a 2016 project as a 2014 file, Sketch Up 2014 says it was saved in the wrong version. When I reopen that file in Sketch Up 2016, it says that it is a 2014 version and will be upgraded to Sketch Up 2016.
From SketchUp (SU) 2016, use File Menu → Save as …
Choose SketchUp version 2014 (*.skp) in the pull down list.
Click Save.
Make sure that you start SU 2014 before loading the file or right click the file and make sure that your OS offers you SU 2014 as the default application for opening skp files.