My read is in the context of "trying to get a job".

To get a job, you gotta match an unfilled position with a person.

This either happens through a company re-hiring for the same position because of attrition, or a net new job created that you can fill.

This graph shows the latter.

You can roughly interpret this graph as showing the net-success of people entering that workforce.

So, if you're trying to get into the field, this is painting a bleak picture that in general, people are unable to enter the field (at least without at LEAST one person exiting it)