How Many Vampires Exist?

From the Congressional Committee on Non-Human Involvement in the Global Economy:

Unknown. Prior to the Attacks of October, vampires were believed to be extremely rare in this country. Estimates now range from one or two to several dozen per major metropolitan area. The Attacks proved that a very small number of vampires can cause immense damage to the national economy—with severe disruptions to business, societal, and governmental functioning—while causing relatively few deaths and little property damage. Perhaps the greatest harm from the Attacks and their aftermath has been to the societal intangibles of safety, morale, and freedom.