After An Lushan’s Rebellion, it is the key factor of production of the semiannual tax law that the relative bargaining power of Tang dynasty has been reduced. It is the prerequisite for its development that transaction costs has been reduction. And it is the low discount rate that ensures its advantages. However, it is the constraint of relative bargaining power of the Tang dynasty that is an important factor for the late and inefficient semiannual tax law, reduction of the transaction costs will ultimately shift the burden on the people, and produce a variety of drawbacks. Low discount rate is also difficult to achieve under the influence of the war. The semiannual tax law of Tang Dynasty can not save the fate of its decline. Obviously, there are two sides of the impact that the relative bargaining power, transaction costs and the discount rate for the revenue policy of the Tang Dynasty. It promotes reform and development of the semiannual tax law, but also caused limitations, defects and inefficient of the enforcement of the semiannual tax law.% 安史之乱后唐政府相对议价能力的削弱是两税法产生的关键因素，交易费用的降低则是两税法发展的前提，而低贴现率则保证了两税法的先进性。但是，唐政府相对议价能力的制约作用，又是两税法迟来和低效的重要因素，交易费用的降低则最终将负担转嫁于民众，产生了种种弊端；低贴现率在战争的影响下也最终难以实现，唐代的两税法并不能挽救其走向衰落的命运。显然，相对议价能力、交易费用和贴现率对唐代岁入政策的影响具有两面性：它既促进了两税法的改革和发展，但同时也是造成两税法执行力度有限、弊端和低效的重要动因
展开▼
