Big 3 uni grads don't want to join big 4. Big 4 is their last option. My big 4 firm can only hire private uni grads or work permit holders. Most seniors in my big 4 firm are work permit holders. locals usually quit once they reach senior.the firm knows that work permit holders are easier to be exploited and they also know that private uni grads will be more committed since getting into big 4 is considered a major achievement for private uni grads but a shame for big 3 uni grads