Debate has long raged on the best way of increasing the number of women at the top of companies: legislation or voluntary targets. In Germany, the answer is: both.

A law passed in March 2015 required the country's 100 largest listed companies to have women in 30% of board seats starting early in 2016. But in an intriguing twist, it also required a further 3,500 mid-sized corporates to publish a voluntary target in September 2015 stipulating their own targets for female representation on boards and executive committees sitting below the supervisory board level.