My first point would be that on what basis do you say a 10%...

My first point would be that on what basis do you say a 10% staff turnover rate is not optimal. If I could replace my entire workforce with team members that are cheaper based on age (most awards start at 12 years of age & increase per year until considered a senior (18-21)) then I would be endeavouring to control my labour cost. Productivity increases will only get you so far & eventually you will need to reduce wage cost trough other means. Whilst it is illegal to advertise & hire based solely on age I think you will find that if 2 applicants (1 a junior & 1 a senior) are vying for the same position it would most likely go to the junior. That's just good business sense. Having managed a QSR (Quick service restaurant) for over a decade it was incumbent on me to recruit team members at a young age, even if I had sufficient personnel numbers, to give hours to in preference to older staff (often forcing them to seek work elsewhere). Now, having said all that I think you need to reassess your staff turnover calculation. With 360 stores (your number) & 18 positions advertised (your guesstimate that there would be an equal number advertised internally is flawed in that any transfer within an organisation is not considered turnover unless the original position is filled externally) this is a turnover of 5%. This is only true if each store employs just 1 team member. All your numbers indicate (18 positions & 360 stores) is that 5% of all stores are currently looking to fill 1 position. So what?