The following are approximate tallies of current listings by county. These counts are based on entries in the National Register Information Database as of April 24, 2008[2] and new weekly listings posted since then on the National Register of Historic Places web site.[3] There are frequent additions to the listings and occasional delistings and the counts here are approximate and not official. New entries are added to the official Register on a weekly basis.[4] Also, the counts in this table exclude boundary increase and decrease listings which only modify the area covered by an existing property or district, although carrying a separate National Register reference number.