P1ss takes apart, I was surprised about this figure for two reasons:
Firstly, if you give a cross section of servicemen a survey, many presume the results might be used to change/improve things, so if they're asked "are you paid enough?" they'll generally reply "no" in a vain attempt to influence a pay rise. In the same way, some think that by voicing their plans to exit this will prompt bosses of various levels to panic and instantly try and resolve whatever grievances are the flavour of the day. To some degree this used to be true 15+ years ago, but now in more cases than not the bosses are either primarily focussed on their own career or, like their blokes, looking at the exit for the same reasons. So I'm surprised the figure is only 50ish%.
Secondly, when I first joined people occasionally put their notice in/PVRd and even discussing a future post-Service was viewed as most disloyal. Today most people openly talk about looking forward to their next option point, and the remainder tend to be junior ranks who haven't thought too hard about the future yet, ambitious officers who are often transfixed by getting as high as they can before pension point, or a handful of 'lifers' who genuinely enjoy the job/life or are stuck because of BSA etc. But that's still only about 10-20% of people I know.
< half doesn't seem to represent the mood.