In a number of instances, survey questions asked respondents to estimate the percentage of gangs or gang members who were involved in a particular activity or who met certain criteria. Specifically, this pertains to the questions regarding drug sales and distribution and gang migration. An important limitation to interpreting these types of responses is that these percentages do not reflect differences in the number and size of the gangs across the reporting jurisdictions. To account for this important factor, the percentages were weighted by the total number of gangs or gang members (whichever was appropriate) reported in each jurisdiction. Only the responses of agencies that reported both numbers of gangs and gang members were used in this weighting procedure. This requirement decreased the number of agencies included in the analysis but increased the reliability of the translation of percentages into actual numbers of gangs or gang members.

Although weighting is necessary when reporting aggregate estimates of gangs or gang members, it is also important to be able to make comparisons about gang activity across jurisdictions using the variables discussed above (area type, geographic region, and population). Therefore, the remainder of the analyses were conducted by comparing averages for each jurisdiction, regardless of the size of the gangs in each jurisdiction. This procedure allowed differences across jurisdictions to be observed without being skewed by jurisdictions with a disproportionate number of gangs or gang members. When appropriate, tables are included in the following analysis to illustrate the differences between weighted and unweighted averages.