Part of the reason why the vast majority of recruitment advertising delivered low result is because the demographic data required to plan proper targeting strategies seldom exist. Say, if one doesn’t know the makeup or the supply and demand dynamics of the PHP community it will be difficult to plan and pull off a successful recruitment campaign.
Instead, blame is often laid on the middleman (e.g. job boards, print etc) when essentially the problem is planning and targeting flaws as a result of poor availability of data. Any amount of advertising on job boards is not going to work if the demographic one targets do not frequent them. Paucity of data is the main culprit.
Numbers do not explain everything but they allow us to form perspectives and can help in the shaping of effective targeting strategies. Any day, it’s better than guesswork.
ACS is one of the leading professional associations regularly churning out good data on the IT industry. If you are in the business of hiring IT professionals, at the very least peeking at their comprehensive compendium (pdf) will assist in forming clearer perspectives, which can be valuable in planning targeting strategies.