Does the data reflect true geographic boundaries or just USPS boundary definitions?<p>USPS addresses are based on delivery convenience and may not accurately reflect underlying political boundaries.<p>For example, in the San Jose area, there are many Los Gatos addresses that are actually in Saratoga (or unincorporated land) and vice-versa.  There are even properties with Los Gatos mailing addresses that are actually <i>outside of Santa Clara County altogether</i> (in Santa Cruz).