Final answer:
It is true that union density is significantly higher in Western Europe compared to the United States, due to Europe's stronger labor union traditions and the decline in US union membership.
Step-by-step explanation:
The statement that union density in most of Western Europe is significantly greater than in the United States is true. Union density refers to the proportion of workers who are union members, and it tends to be higher in European countries than in the US. Many European countries have strong traditions of labor unions being integrated into the economic and political systems, which contributes to higher densities. In comparison, the US has seen a decline in union membership over the past few decades, leading to lower union density.