One problem associated with an ageing population is that health care costs will escalate,imposeing a burden on taxpayers.
associated此处是作后置定语吗?
应该是 associated with an ageing population 这个过去分词短语作后置定语,而不是associated这个过去分词作后置定语。分词短语、形容词短语等作定语时应该后置(即把整个短语放在它所修饰的名词后面)。