Demand for US sperm is on the rise. Not just American; Danish semen is also used by women around the world. The reasons are as varied and distinctive as each country’s own regulations and approach to bioethics and business.

Sperm from the US and Denmark dominate the market because those countries currently have the most supply, experts say. It’s unclear whether their rivalry is serious or in jest, but US-based California Cryobank and Denmark’s Cryos International each insist that their sperm repository is biggest.

California Cryobank claims it is the largest sperm bank in the world by “any metric”; Scott Brown, director of client experience, noted that the firm has a pool of roughly 600 donors and a track record of 75,000 live births globally since 1977. The company has locations in Palo Alto, Los Angeles, Cambridge, Massachusetts, and New York.