Vacancies may impact new recruiting because vacancies send a message to future recruits that we are not easily able to recruit replacements. Large numbers of vacancies may also send a message to our current employees we are headed down hill. High vacancy rates may over-stress our recruiters and recruitment process. If hourly employees are involved it probably means additional overtime costs. Vacancies can mean the underutilization of plant and equipment.
New hires are unlikely to be immediately productive, thus resulting in increased costs.
Many new hires don't work out and must be replaced within 6 months, essentially stretching the length of the vacancy. In a tight labor market vacancies in hard to hire jobs may not be replaceable, at any cost. In start-ups and small departments, where there is little cross training, the cost may be more dramatic.