It is specified in the Governance - Collective Bargaining Chart p94 & People - Freedom of association and collective bargaining at risk (%) p109 :

"JLL employees are free to join or participate in a worker’s association or union in accordance with local law. Generally we are not able to report this

information in majority of the countries we operate in due to labor union memberships being considered a private matter of the employee. The

exception is approximately 3,100 property maintenance employees in the United States, 78% of whom are reimbursable."