My suggestions would be to compare data sets of the same seasonal preiod. I.e Qtr 4 2009 with Qtr 4 2010. Otherwise you could be introducing a bias in your analysis. It might be known that a certain time of year i.e. summer has a better clearance rate for properties than in winter. You need to be clear in avoiding such facotrs to influence your conclusions.

If you do want to make some inferences between data sets that have a different sample size (and in your case a very small sample size) you can employ a 2 sample t-test for differences in the mean.

Have a read

Unpaired (two sample) t test

1.3.5.3. Two-Sample <i>t</i>-Test for Equal Means

What do you think?