It's safe to assume that EV training has been revolutionised in Sun and Moon. A called ally Pokemon will have yield double the EVs its species would usually give; this EV yield continues doubling as more ally Pokemon are called. For example, if a Golduck were to be called, it would give 4 Sp. Atk EVs instead of 2. If one of the original Pokemon are defeated and another Golduck is called, that Golduck will yield 8 Sp. Atk EVs. This process will goes on and it allows a stat to be fully EV-trained with merely seven defeats! Better yet, these EV yields are further doubled with Power items and PokeRus.
And here is a comprehensive list of every Pokemon's EV yield, correct as of Generation VII.
Hope I helped. :)
Source: Expeirence and above link