At one time non metallic sheathed cable commonly known by the brand name "Romex®" formerly made by General Cable, now made by Southwire, had a 16 AWG ground wire in 12 and 14 AWG sizes, sometime after the adoption of the 1968 NEC, it was required that the grounding conductor in 10,12,14, AWG sizes that the grounding conductor be the same size as the insulated conductor in those sizes, 6 and 8 AWG NM cable have a 10 AWG grounding conductor, my house which was built in a factory in 1943, was wired with a early NM cable, plated copper conductors, insulated with rubber, covered in cloth, with a spiral paper wrap over each individual conductor, jute string fillers wrapped with a asphalt covered cloth sheathing, the stuff is still in pretty good shape considering how many years since it was manufactured, although it's been of service since around 1980.