上周五，在欧洲交易的西班牙与意大利的国债收益率小幅回调，原因是市场指望法国和德国能拿出有效的方案，收拾当前的烂摊子。
Spanish and Italian bond yields rallied slightly in European trading on Friday on the hopes that France and Germany will come up with some sort of solution to the current imbroglio.
广告主要的是切实有效的结果；他们想跟踪收益率，一次点击对他们来说并不算是收入。
Advertisers want actionable results; they want to track their ROI, and a click is not revenue to them.
根据马科维茨的定义，有效组合是指其单位收益的风险最小或单位风险的收益率最大。
Optimizing portfolio is that the least risk in an unit return or the most return in an unit risk on the basic definition of Markowitz.
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