Final answer:
Cooperative federalism has been the most common type of federalism in the United States since 1980.
Step-by-step explanation:
The type of federalism that has been most common in the United States since 1980 is cooperative federalism. Cooperative federalism is characterized by both the national and state governments working together to solve national problems. It erodes the jurisdictional boundaries between the states and the national government, resulting in a blending of layers as in a marble cake.
In a cooperative federalism system, the federal government provides funding and resources to the states to support the implementation of federal policies. State governments have some flexibility in how they implement these policies, but they must still comply with federal guidelines. Thus, this model of federalism has been predominant since the year 1980 and has led to the expansion of the national government's power in concurrent policy areas.