In just comparing two years, you could do it with a simple chi-squared test (PROC FREQ).
In looking at a longer time period, you might best do that with a logistic regression model treating year as a predictor variable (that would look for a linear trend in the change). (The MEASURES option in PROC FREQ will do ordinal association, to look at a monotonic change.)
Thanks. When looking at % low birth weight between two years I just compared the overall average: 2005 at 7.7% and 2006 at 7.9%. When I plug this into proc freq/chisq it thinks I only have two observations, which I can understand why sas thinks that based on my number of observations but in reality LBW is calculated from thousands of records. How can I overcome this without putting every observation in sas?