To expand, Disney follows a pattern - they have to estimate dues when they start selling a resort. They are obligated to make a good faith estimate, but its in their best interest when selling a resort to estimate low - and they do.
Once a resort has a year of operations under its belt, then they have real numbers to work with, and they adjust - but because they don't have a fully operational resort, they are still using some estimates - and whenever they have to estimate, they go a little low - its good for sales.
So for the first year, dues are low, then dues spend a few years going up more than average, and then they level out.
That's a logical (and safe) assumption to make but the numbers really don't demonstrate that pattern consistently.
Here are the first 5 years of dues increases (by percent) for the most recent WDW resorts:
VWL: 0.2 | 4.6 | 6.6 | 4.2 | 3.0
BCV: 5.3 | 5.2 | 2.1 | 4.9 | 3.3
SSR: 1.0 | 3.9 | 3.5 | 2.2 | 3.1
AKV: 1.9 | 3.1 | 2.5 | 1.2 | 8.5
BLT: 2.9 | 2.9 | 8.4 | 6.5
VWL and BCV did have sharp increases early on but more recent resorts did not.
One could argue that DVC intentionally delayed increases while resorts were still selling but that's an imperfect assertion. The 2011-12 increases for AKV and SSR were their highest ever (the 8.5% above for AKV and 4.9% for SSR) but both resorts were still in active sales at that time.
Now SSR is finally out of active sales and the 2013 increase is one of its lowest ever at 1.7%.
Meanwhile that first year BCV increase of 5.3% came while points were still being sold.
The recent increases of 8.5% at AKV and 8.4% at BLT were inflated due to a recalculation of the villa/hotel guest mix at those two shared properties.
I agree that it's in Disney's best interest to estimate low. The SAFE assumption to make is that there will be higher-than-expected increases early on as estimates become reality and resort operations are adjusted.
But overall I'm not sure there's really a pattern. Just looks like some estimates have been better than others.