This report provides a comprehensive analysis of the significant decline in trade union membership in Australia over the past two decades. It explores the changing industrial relations environment, including legislative changes, the rise of workplace-level agreements, and the impact on union power. The report examines the decline across various demographics, including age groups, sectors, and employment types, highlighting the shift towards part-time and non-unionized employment. It delves into the structural changes in the labor market, institutional factors, and new employer strategies that have contributed to this decline. The report also compares Australia's unionization rates with those of other OECD countries and discusses the implications of these trends for Australian society. The report concludes by considering the future of unions and the challenges they face in a changing economic and social landscape.