820 ILCS 65/25

In determining whether a plant closing or mass layoff has occurred or will occur, employment losses for 2 or more groups at a single site of employment, each of which is less than the minimum number of employees specified in subsection (d) or (f) of Section 5 of this Act but which in the aggregate exceed that minimum number, and which occur within any 90-day period shall be considered to be a plant closing or mass layoff unless the employer demonstrates that the employment losses are the result of separate and distinct actions and causes and are not an attempt by the employer to evade the requirements of this Act.