I dug the stats out of the Ryanair annual reports when it used to disclose the split between direct hire and agency flight crew. The first graph has the real data, the second includes projected numbers for 2012-2017 if the direct hires stayed at the same level (in reality there will have been growth, so I'm just mucking around). That results in a 74% agency / 26% direct hire split by 2017. Which has the former too high I reckon, but it won't be miles off (it's about right for cabin crew, but high for pilots, so overall...).
The interesting thing for me is that Ryanair's heavy reliance on agency/indirect employment is actually relatively recent (the majority of Ryanair flight crew were direct hires within the last 10 years), and has grown significantly in recent years. So it has continued to push the barriers on labour practices even as it has grown, rather than these being small/cowboy operator practices that got it started but which might be phased out when it got to scale. (Though that might start to change now). Bear in mind too the funky stuff that has done with pilot 'self employment' in the past few years.