Why is onboarding important? If for no other reason, it’s because corporations do it more frequently than ever.

The statistics speak for themselves — according to the U.S. Department of Labor, more than 25 percent of the U.S. workforce has been at the same company for less than one year. Younger workers today will change jobs an average of 10 times before they turn 40. Recruiting consultancy Spherion reports 45 percent of all workers want to change jobs every three to five years.

Mergers and acquisitions also drive the need to bring aboard many individuals within a fairly small window. Achieving a Day 1 integrated workforce requires intensive planning and execution on multiple levels, including culture, training and human capital governance.

This is especially true in that, according to Mellon Financial Corp., the average time to full productivity is eight weeks for clerical jobs, 20 weeks for professionals and 26 weeks for executives.

Also consider the consequences of failed onboarding. The Labor Department has found employees are most vulnerable to leaving an organization for 18 months after they are hired. At the very least, failed onboarding means losing the direct costs of recruitment, which (according to Staffing.org and the Bureau of National Affairs) range from about 5 percent to more than 21 percent of annual compensation.

The Institute of Industrial Relations at the University of California, Berkeley, estimates the total cost of employee turnover at 150 percent of salary, including tangible costs such as hiring, as well as intangible costs such as the ramp-up time and lost productivity while the job is vacant.

Onboarding must be a key human capital priority, not just for the human resources function but for senior leadership. Indeed, today’s senior leaders must play the role of onboarding sponsors and be prepared to set strategy and direction for successful programs. This includes providing both financial resources and their own personal attention.

Some of the emerging onboarding issues with which senior leaders must be engaged are: