Yes, dominant. But that doesn't mean it's the original spelling. The name originates from England so as
Hayley is the standard spelling there, this might be how it first appeared. I don't want to find out the most popular spelling, but the original one.
Hailey is not a
German name. For example,
Allison is way more popular than
Alison but
Alison is the original.
Collin and
Connor are more common than
Colin or
Conor, but
Colin and
Conor are the originals.
Kaitlyn is way more common in the US than
Caitlin, but
Caitlin is the original. I feel like the UK is more likely to stick to originals (
Caitlin is the most common spelling there). Interesting to think about this. Thanks for your reply :)