[简答题] In order to (47)______ unemployment and why it happens, economists often split unemployment into the following four types. Demand-deficient unemployment (48)______ when there is not enough demand to employ all those who want to work. It is also often known as cyclical unemployment because it will vary with the trade cycle. When the economy is (49)______, there will be lots of demand and so firms will be employing large numbers of workers. Demand-deficient unemployment will at this stage of the cycle be fairly low. If the economy slows down, then firms will begin to (50)______ workers off as they do not need to produce so much. Demand-deficient unemployment rises. Seasonal unemployment is fairly self (51)______. Father Christmas tends to only be in demand for a short period of the year, and the rest of the year would certainly be (52)______ as seasonally unemployed. Most other seasonal unemployment is less (53)______ than this, and tends to occur in certain industries, suc