In cities where sexually assaulted victims get health treatment, psychological counseling and free meals and housing for two days, reports of having suffered a sexual attack are twice as frequent as they are in cities where this benefit is not present. Presently, no accurate test for sexual assault exists, so it is true that spurious reports of sexual assaults cannot be readily identified. Nevertheless, these facts do not warrant the conclusion drawn by some commentators that in the cities with the higher rates of reported sexual assaults, half of the reported cases are spurious. Clearly, in cities where sexual assault victims do not receive counseling, treatment, housing and meals following their incident, people often have little incentive to report sexual assaults that they actually have suffered.
In the argument given, the two boldfaced portions play which of the following roles?