Sex Trafficking Demand Reduction Act This bill expands requirements for fighting human trafficking that apply to foreign countries receiving U.S. foreign assistance. (The President is authorized to reduce assistance to, or take other actions against, countries that fail to meet such requirements and are not making significant efforts to do so.) The Department of State, when evaluating whether a country has met such requirements, shall assess whether the country has made serious efforts to prohibit the purchase of commercial sex acts if the government has authority to do so, whereas currently the State Department must assess whether a country has made serious efforts to reduce such activities. The State Department shall also assess whether a country has made serious efforts to (1) educate buyers of commercial sex acts on how traffickers exploit prostituted persons, and (2) ensure that anti-trafficking training and provisions are incorporated into codes of conduct for government staff.