[gerbilly]

Sure but presumably, unless all employees start out only at your company, then the effect would also sometimes happen in your company's favour.

As I said in point #1, as long as the rate of defections/arrivals is about even, then your losses on one employee would be offset by your gains on others.

[thereisnospork]

Having an even defection/arrival rate requires other companies to also train their employees, and not only hire previously trained persons.