▁Category : 1 9 9 1 ▁establish ments ▁in ▁Texas <0x0A> </s> ▁In ▁social ▁choice ▁theory , ▁the ▁Gib b ard – S atter th wa ite ▁theorem ▁is ▁a ▁result ▁published ▁independently ▁by ▁phil os opher ▁All an ▁Gib b ard ▁in ▁ 1 9 7 3 ▁and ▁econom ist ▁Mark ▁S atter th wa ite ▁in ▁ 1 9 7 5 . ▁It ▁de als ▁with ▁determin istic ▁ord inal ▁elect oral ▁systems ▁that ▁choose ▁a ▁single ▁winner . ▁It ▁states ▁that ▁for ▁every ▁voting ▁rule , ▁one ▁of ▁the ▁following ▁three ▁things ▁must ▁hold : ▁▁ ▁The ▁rule ▁is ▁dict atorial , ▁i . e . ▁there ▁exists ▁a ▁distinguished ▁vot er ▁who ▁can ▁choose ▁the ▁winner ; ▁or ▁ ▁The ▁rule ▁limits ▁the ▁possible ▁out comes ▁to ▁two ▁alternatives ▁only ; ▁or ▁ ▁The ▁rule ▁is ▁sus cept ible ▁to ▁tact ical ▁voting : ▁in ▁certain ▁conditions ▁some ▁vot er ' s ▁s inc ere ▁ball ot ▁may ▁not ▁defend ▁their ▁opinion ▁best . ▁ ▁While ▁the ▁scope ▁of ▁this ▁theorem ▁is ▁limited ▁to ▁ord inal ▁voting , ▁Gib b ard ' s ▁theorem ▁is ▁more ▁general , ▁in ▁that ▁it ▁de als ▁with ▁processes ▁of ▁collect ive ▁decision ▁that ▁may ▁not ▁be ▁ord inal : ▁for ▁example , ▁voting ▁systems ▁where ▁vot ers ▁assign ▁gr ades ▁to ▁candidates . ▁Gib b ard ' s ▁ 1 9 7 8 ▁theorem ▁and ▁Hy ll and ' s ▁theorem ▁are ▁even ▁more ▁general ▁and ▁extend ▁these ▁results ▁to ▁non -