I have two polygon shapefiles--blocks groups (BGs) and neighborhoods. Generally, BGs are smaller than neighborhoods. Sometimes they lie entirely within a neighborhood, but often they overlap two or more.
I can merge these so that the first joining attribute (neighborhood) is retained, but this isn't what I need. How can I join these two files so that the attribute table contains a row for each BG-Neighborhood pairing, with a variable giving the proportion of the BG contained in that neighborhood?