Overall, two-thirds of non-regular workers are women. Data from business and labour force surveys since the 1990s (JILPT, 2009a) indicate that an increasing proportion of employers cite reducing labour costs as the most important reason for hiring non-regular employees, regardless of their particular category. Indeed, firms can save wage and non-wage costs by paying workers less on an hourly basis {e.g. in 2006, part-time workers were paid only 40% of hourly wages of full-time workers), by paying lower or no bonuses and retirement allowances, and by using current exemptions of certain worker categories from health, pension and El contributions.