Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:While the general decline in MVT deaths rates has been associated with multi-pronged prevention efforts as well as reduced driving among older adolescents (2,8), the sharp drop beginning in 2007 has also been associated with the economic recession in the United States (9).
Category: