Each project has its own productivity. I know that for certain customers the productivity is always lower than the trendlines from QSM or ISBSG. There are several reasons for this, like: complexity of the project/environment, time pressure, lots of CRs getting approved, etc.
If you compare against those situations, it will be hard to prove productivity/comparing companies, so you might easily choose the wrong one.
QSM NL has a statement on one of the walls inside there building, it looks like this: ‘If you focus on productivity you will loose quality, if you focus on quality you will gain productivity’.