![See below for text description [D]](/peth04/20041108075516im_/http://www.ahrq.gov/data/safetynet/philfig3.jpg)
[D] Figure 3 is a map of southeast Baltimore that includes Fells Point, Canton, Patterson Park, Johns Hopkins Hospital, and Hopkins Bay View Hospital. It uses both clinic and census data to reveal the proportion of people in each census block group that use the Baltimore Medical System Highlandtown clinic. In approximately 13 of these block groups, between 15 and 27 percent of the population made visits to this clinic in 2001. In an even larger number of block groups, more than 5 percent of the population used the clinic, including one on the opposite side of the harbor. The "penetration" map offers a sense of a clinic's market share for neighborhood populations which may be useful for a variety of applications.