A possible "Rule" element to represent the relationship between the rate of illegal immigration into the United States and identifiable key variable factors could be:

"If the levels of identifiable key variable factors such as economic opportunity, political stability, and security in countries of origin and the effectiveness of border security measures and immigration policies in the United States are favorable, then the rate of illegal immigration into the United States is likely to be lower. Conversely, if these key variable factors are unfavorable, then the rate of illegal immigration into the United States is likely to be higher."

This rule suggests that the rate of illegal immigration into the United States is influenced by a combination of push factors in countries of origin and pull factors in the United States, such as economic opportunity, political stability, security, and the effectiveness of border security measures and immigration policies. By considering these key factors, policymakers can develop more effective strategies to manage and reduce the rate of illegal immigration into the United States.