The explanation for the "ratio change" can be found at the top of ITC's fB Page.
In short: If you liked 50/50, get the 60/40.
All ratios are PG/VG
There seems to be a lot of concern from the tank users about our recent switch to 60/40. Please let me clear up a few things. In the past we continually received complaints that our 50/50 blend was too thick and did not wick properly with a CE4, evod, etc tanks. We changed to 55/45 and recently to 60/40, which is the most consistent to the market standard 50/50, yet continued to call it 50/50 to avoid confusion. We just released new labels and we considered keeping the name 50/50 but really wanted to be able to call it what it actually is...a 60/40 that vapes like 50/50. With that said, you can rest assured that the "new" 60/40 will vape no differently than the old 50/50.
In short: If you liked 50/50, get the 60/40.