I read this as: 18% of 110 is 20. If they started with
4 and hired 18, that would be a "four and half times"
increase (perhaps modulo replacement or non-FTE hires).
In any case, good for Etsy for investing in training
rather than just spending placement fees.
Seems like a grammatical error in the article. They have 20 now, which is about 18% of their eng team, and I guess they had 4 to start with. This is ~+450% growth but it's off such a negligible base (~5% assuming they also hired some men that year) that the whole "500% growth" claim is only interesting as a marketing statement, so it kind of undercuts the rest of the article's value.
It's like a school with one minority student out 100 letting in two more and then bragging about "200% growth in minority students."
I'm not taking away from what they did - just how they're positioning it based on a growth figure.
In any case, good for Etsy for investing in training rather than just spending placement fees.