I'll post this link again. Everyone interested in this topic has to read that article.
There is, however, plenty of expense that comes with managing an employee’s year-long absence, starting with finding a temporary replacement. Job advertising costs, plus the fees for a recruiter to scout for candidates, review resumés, interview, do reference checks and negotiate the offer terms are just the beginning. Add to that training expenses for the newcomer. And if there’s an overlap between the temporary and the outgoing employee to ease the transition, companies pay double wages and EI contributions for that period. “Even if an internal person fills a mat leave, there’s the domino effect within the organization,” says Margaret de Gruchy, a recruitment and retention specialist in B.C., “because while Sally is filling the temporary position, Sue has to fill Sally’s job, but then who will fill Sue’s job?”