Here are mohican/VHB's charts for housing starts, housing completions, and under construction, as well as graphs showing how they compare to population growth.
The last few months have seen a continued dearth of completions and an increasing amount of starts and under construction volume. Starts will typically lead completions by about 12 months so we should expect to see increased completion volumes heading into the first and second quarters of 2012. Given that completions are still low compared to pre-recession levels I expect this to provide some constraints on new supply for the first half of 2012 ceteris paribus, however other factors including investor sales, lower population growth, and downsizing are likely to at least partially counteract, if not fully swamp, this. As 2012 progresses and completions increase this will naturally tend to increase supply.