We are currently using a GIS (ArcView 8.3) to assist in re-designating our urban growth boundary and want to use the 1990 and 2000 Census blocks to determine population change (so that we can predict where future growth is going to occur). Using the Census 2000 block relationship files, we can examine how the blocks from the two censuses compare (i.e. one-to-one, one-to-many, etc.). However, in order to do a direct comparison between the 1990 and the 2000 blocks, we need to have a comparable geometry between the two datasets. For example, if you have a one-to-many relationship within a particular block unit, the "many" 2000 blocks need to be aggregated to match the "one" 1990 block and visa versa with the many-to-one relationship. In a sense, a "cluster" database will be created which will include all the one-to-one blocks and also all the aggregated blocks. I have done various intersects and dissolves within ArcView, but have not been able to create a database that globally aggregates the smaller units into the larger units successfully. If any GIS'ers can offer some advice, it would be greatly appreciated. Also, have any MPO GIS'ers analyzed block level population changes around their boundaries to forecast which fringe areas will likely fall into their MPOs in 2010? Cindy Pellett Bangor, ME