Worldwide, 112 spider families are recognized so far. North America currently has representatives of 71 of those (as of 2013). Taxonomy is a fairly fluid thing; as more information is gained about spiders, new families are created or split apart or transferred to other families, so these numbers are always subject to change. Sometimes taxonomy is debatable, with different researchers taking different positions as to what belongs where. More often than not, however, there is agreement at the family level.