Flow charts can reveal which criminal method is used most and least after criminal incidents are plotted on the chart and calculations are made. Policies can then be devised to meet the crime problem. Flow charts can also identify the population at risk if the chart is keyed, for example, to suburbs v. central cities, and not to the method of entry. A ranking scheme reveals general trends in specific types of crimes and is popular with agencies because it is simple to calculate and a good method of starting the crime analysis. The ranking scheme breaks down various crimes by local, Standard Metropolitan Statistical Area, division, region, and national levels. Time-series analysis, incorporating trend analysis, cyclical effects, seasonal analysis, or regular effects, projects crime levels. Trend analysis can show monthly/yearly fluctuations using the straight line method, cyclical analysis uses 'moving averages' to depict trends in crimes that reoccur over time, and seasonal analysis shows fluctuations that reoccur over time and within the confines of 1 year. Analysts using survey data should be concerned with the time and costs involved and data reliability. Social indicators can also be used to analyze crime trends. In Washington, D.C., analysts constructed social indicators by first running correlations on Index crimes and then doing principal components analysis on the results and reducing the Index crimes to one measurement (a scatter diagram). By color coding values from the cluster analysis on a district map, planners were able to see which crime control measures were best in different parts of the city. Criminal geocoding, in which criminal events are listed by geographic location, is a new tool for planners. It can be used in computer-assisted dispatching, investigation support, crime analysis, and other areas.