Depends on the manufacturer.
BMW and Merc are losing out because of this, their discounts vary an aweful lot. Take Mercedes as an example, one month they will offer standard dealer discount, the next they'll be giving registration bonus' of several thousands. It's knowing when to buy that is important where these are concerned.
For example my car is only a C180 but there was a discount of approx. £4500, a couple of months later this had dropped back to just under £2000. This money has to come from somewhere on the second hand market. A trader will always bid you on the worst case because they are aware what they were going for either a few months prior or at that particular moment in time, if a trader pays low money, it reflects on their forecourt prices which in turn moves onto the private used car buyer.
Next up... Ford, vauxhall, citroen, renault etc. Why are the residuals so awful? It is not uncommon to see discounts of over 20% on any one of these vehicles if you know where to look, and no I'm not talking about imports, these are for UK cars. Some traders are dodgy enough to access these on a courtesy car scheme that gives even more discount and so as you can imagine this has an impact on the used market.
Chrysler... I've put these on their own purely for one vehicle. The 300C. They made such a big deal out of how they weren't going to offer any discount to help bring the marques residuals back up in line with the competitors on the market... what ever happened to that? It was a good plan but it's all gone to sh*t now they're happily discounting the cars!
Audi/VW - Spot on, they have the best marketing campaigns by far. Everything is tight under wraps and they sell discontinued models right up until the day the new vehicles are released. For example... how many of you can say you knew the A4 cab was being discontinued? That there is a new A4 out in about 7 months and what it looks like besides a few speculative photoshops? They really do have it spot on.
Well anyway... the good thing about VW and Audi is you go to them one month and the discount is £x, go back 6 months later, its still £x. This is VERY important. The only time they change is when they become a "niche" product as they put it ie. when the car is first released they offer lower discounts because the retail lads can knock them out at full whack. Or at the other end of the scale when a product is being discontinued, rather than blow the back out of them they actually reduce available discounts in order to strengthen the residuals slightly for when the new shapes are released and wow does it work!
With this in mind, I say its a 50/50 split with manufacturers caring
move the metal 
