As a rule of thumb for social science writing, on-going issues and current realities should be reported in present tense. What has occurred, what has been reported, and what you and others have accomplished should be reported in past tense. That is, if health care costs no longer are a problem, or if oil imports are no longer increasing, past tense works. Otherwise, as ongoing realities, they should be described in present tense. In the review of literature, most writers choose to use the past tense.
Some writers refer to past research in present tense.