According to a very highly upvoted post on Workplace.SE that says you should never accept a counteroffer:
80% of people who accept counter offers are gone from that company within 6 months, at the 12 month mark that goes up to 90%
I looked at the sources that the post cited:
Source 1 says “70-80% of people who accept either leave or are let go within a year”, but it gives no reference for those numbers.
Source 2 says “According to national surveys of employees that accept counteroffers, 50%-80% voluntarily leave their employer within six months of accepting the counteroffer because of promises not kept. The majority of the balance of employees that accept counteroffers leave their employers within twelve months of accepting their counteroffer (terminated, downsized, fired, laid off).” But it does not cite exactly what surveys those numbers come from.
Source 3 says “80% of all employees who accept a counter-offer are no longer with that employer after 1 year”, but it gives no reference for that number.
Source 4 says “statistics show that 80% of people who have accepted a counter offer will not be at their current employer in six months and 93% will not be there in eighteen months’ time”, but it gives no reference for those numbers.
Is there any reputable source that can back up the claim that about 90% of employees who accept a counteroffer from their current employer will be gone from that employer within a year?