I did some rough math for Jan 2016 to Jan 2017 and I saw approximately 330 hired against a net gain of approximately 180.

Also, only looking at those hired for Jan 2016 to Jan 2017, the attrition is about 10%.

Overall attrition during that period averaged about 12 per month. I know of at least one 20 year CA who has his apps out and is committed to leaving.