This 'scissor diagrams' are a gross misrepresentation of what is really going on in academia. It conveys the the misleading message that 'the pipeline' is only leaking for female STEM aspirants. In fact, if you start with 100 woman and 100 men, so 200 STEM students in total, only around 1-5 people will make it to the end of these scissor diagrams (professorship and alike). Let's assume a very strong imbalance, say we have 4 man and 1 woman making it (80/20). That means the drop out rate (or 'leakiness') is 96% for men and 99% for woman! So yes, in this case it is 4 times as likely for a man to become professor compared to a woman. However, it's still very unlikely (4%) for an individual man to succeed and hence the majority of men also drop out of STEM academia.