It's a bit like the ridiculous road death toll stats the media and police churn out every holiday period, where they expect a reduction in the overall number of deaths every year, and yet completely fail to take into account the half million or so people that get added to our population every year (and proportionate increase in number of cars on the road). I guess reporting per capita just wouldn't look as damning, would it? Likewise with aviation, without at least knowing the number of flights from one period to another, the information is meaningless.