In few companies so far I've seen the same scheme - at some point the company pays significantly less than the competitors on the local job market, then staff turnover grows, then salaries for all employees are increased. Is there any standard retention rate at which company should do it?
Is there any specific retention rate at which HR/finance introduce salary increase for all employees?
Every company is different. They all chose their salary scales based on a combination of market rate, availability of workers, and the company's specific financial situation and needs.
There is no magic rate at which everyone's salary would be increased.