The following pages will give you the lowdown on one of the biggest media channels in marketing, in terms of sales and impact on communications effectiveness.
Consumer and business data is the driver behind the £18bn UK direct response industry. Sales of data and accompanying services are estimated to be worth £1bn a year - about the same size as the UK's PR industry.
True, data is under pressure, as is almost every other media, not least because financial services, once the most data-hungry industries of them all, has gone into retreat.
One sizeable straw in the wind is Capital One's recent decision to abandon direct mail as an acquisition channel. With that goes a very large order of data and accompanying hosting and analytical services.
Most of the players included in this survey have felt the pain of losing financial clients, but many have proactively replaced them with other buyers, notably from the telecoms, retail, leisure and utilities sectors.
Other winds continue to buffet the data business. Whereas high-volume, cold postal data was once the sector's mainstay, now warmer, multi-channel lists are the order of the day.
Accurate, opt-in email remains a coveted commodity. Even in these uncertain times, the marketers interviewed for this report say they are willing to pay a premium for e-data that delivers the all-important response they desire.
It's all proving quite an adjustment for suppliers used to selling postal data by the truckload.
Nonetheless, adjust they must, and over the following pages you can judge for yourself which suppliers have made that transition.