What kinds of entitlement programs make it difficult to change spending levels?

Programs such as Social Security and Medicare, since they are a part of the budget that need to be accounted for every year, make it somewhat difficult to make large-scale spending changes. This is especially true with the number of people signing up to claim such benefits increasing every year, as the population who reach such ages continues to grow.

Afine-grained igneous rock forms as a result of slow cooling.