"Vapouround " Magazine ( trade based but available to the public via certain UK Vape Shops such as those in the "Vapourised" Franchise ) issue 03 Winter 2016, page 186 et seq, article "What's in your e-liquid?"
"If an e -liquid was made from 100% VG base it would be very thick and hard to vape effectively which is why most e liquids use a combination of both PG and VG as the base ingredients.
Sometimes a small amount of de-ionised water is added to VG base and in which case it is known as aqueous glycerine (AG)"