The number of sex workers working in Sweden before and after 1999 law reform has been described as "difficult to determine" by Skilbrei. In Skilbrei and Holmström's critical review of the data and reports that have been published, they note that knowledge concerning the size of the market before the ban was primarily based on whom the social workers came into contact with. They conclude that there is "no reason to assume that these represent the market in its entirety." The impacts of the law must also be considered with regard to the way sex workers interact with social workers before and after the ban.