I don't think this is easily quantified.
Look at one of the worlds safest airlines for instance, they are trading on their past record on one hand and cutting the guts out of the company with the other. Culture is a hugely valuable metric in determining a safe operator, but try getting anyone to talk truthfully about their companies culture, all you'll get is a company line about their commitment to safety; they would be too scared of dismissal if they said otherwise!
I think the only true test of an airlines safety record going forward is to observe the CEO and his/her management group. If they are constantly on the box or the radio talking about safety, chances are they are drawing your attention away from the elephant in the room. Or if they regularly talk about their (overly unionised) staff being the cause of all the financial woes while they simulataneously scrape the million dollar cream off the top, chances are you have a failing culture.
And any airline that grows an LCC beside itself, and then puts itself forward as a "host" to the parasite, as opposed to a stand alone airline filling a niche market in their region, is potentially in that "failing culture" basket too.
Essentially, as Capetonian said, flying is safe. Getting to the airport is probably the deadly bit
