According to Bureau of Labor Statistics http://www.bls.gov/iif/oshwc/cfoi/osar0014.htmsurvey, 9 percent of companies with 11 to 49 employees have had at least one incident of workplace violence in the past 12 months, while the rate was 16 percent of companies of 50 to 249 employees and 27 percent at companies with 250 to 999 employees.
There have been several workplace violence issues in the news recently. Read more at http://www.ctpost.com/business/article/Workplace-violence-concerns-HR-professionals-678653.php