Although it is impossible to know the number of individuals who are using SNNAP, several useful metrics can be derived by monitoring activity on the SNNAP website (see http://www.uth.tmc.edu/web_stats/SNNAP/). We began monitoring activity on the website in March 2003, and several of the metrics are summarized below. (NOTE: Statistics given are effective through the latest monthly reporting period. To see these statistics in table format, going back to March 2003, go to our SNNAP Web Statistics Summary page.)

1. Cumulative number of SNNAP downloads.
   Several types of files are available for download at the SNNAP website. Possibly the most critical metric of the number of individuals who are using SNNAP is the number of copies of the neurosimulator that have been downloaded. As illustrated in Fig. 1, since March 2003, 10,694 copies of SNNAP have been downloaded. View Figure 1.
    
2. Cumulative number of SNNAP Tutorial downloads.
   The SNNAP Tutorial has only been available since June, 2003. As illustrated in Fig. 2, since June 2003, 12,554 copies of the SNNAP Tutorial have been downloaded. View Figure 2.
    
3. Number of Visits per Month.
   As an indication of activity on a web site, web sites often display the cumulative number of 'hits' for the site. For example, since March 2003 the SNNAP web site has had over 1.6 million hits. Note, however, that a single visit can generate many hits. Thus, the number of visits is a more accurate metric for the activity on a web site. Overall, as shown in Fig. 3, since March 2003 the SNNAP web site had a total of 69,874 visits by 46,354 unique visitors. View Figure 3.
    
4. Summary of SNNAP Web Statistics
   View Summary of SNNAP Web Statistics, which includes data since March 2003.