一、电子数据交换(EDI)的含义 电子数据交换(EDI: Electronic Data Interchange)开始于20世纪60年代,EDI的含义是指商业贸易伙伴之间,将按标准、协议规范工化和格式化的经济信息通过电子数据网络,在单位的计算机系统之间进行自动交换和处理,它是电子商业贸易的一种工具,将商业文件按统一的标准编制成计算机能识别和处理的数据格式,在计算机之间进行传输
Policy analysis is hard Why is it so hard to tell what's going on with government actions? Consider lowering income tax rates. Will lowering taxes increase work effort and labor supply? · Unlike the physical and natural sciences, difficult to perform carefully controlled experiments on the economy
Externality Defined An externality is present when the activity of one entity(person or firm)directly affects the welfare of another entity in a way that is outside the market mechanism. Negative externality: These activities impose damages on others. Positive externality: These activities benefits on others
Quick Look at Welfare Spending .\Welfare\ in the United States is a patchwork of dozens of different programs. All welfare programs are means-tested-- only individuals with sufficiently low income are eligible. Programs often have other requirements related to family structure and assets