根据有关宏观经济理论,在总需求中,消费在一定时期内比较稳定而变化不大,除非收入有较大的增减;净出口在较长时期内占GDP的比重往往较低,发达阶段的出口导向型国家和地区除外;投资是引起国民产出变化的最重要因素而又多波动,这是由投资的性质和投资乘数作用及加速原理所决定的, According to the macroeconomic theory, among total demand, consumption has remained relatively stable for a certain period of time with little change unless there is a large increase or decrease in income; while net exports tend to account for a relatively low proportion of GDP in a longer period of time, Except for export-oriented countries and regions. Investment is the most important factor that causes the output of the national output to fluctuate more. This is determined by the nature of the investment and the principle of investment multiplication and the acceleration principle.