经济article被教授狂骂太垃圾无法看懂，求大神们授业解惑！
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背景：不怕大家笑话,目前在美国读研究生。
教授给我的评价原文大概是：
"If you are a bad writer, people will believe you are a bad thinker--muddled words are the surest sign of muddled thoughts. You tend to add longer and more exotic words until your idea is lost and you ultimately write something that is false or unsubstantiated. It leads me to believe you want to distract rather than illuminate. "
我写的是对一篇关于IV(instrumental variable)的经济论文的review。我就摘两段自认为问题所在的段落，这两段是在说明为什么此论文的研究不能使用ols模型进行估计。如果哪位大神可以指点迷津，我不胜感激啊。
“Initially if we measure the veteran impact on income using OLS model, the
independent variable would be a binary variable: "whether the person i is a veteran
at time t in cohort c" and the dependent variable would be the person’s
income. Control variables in the model should include all the variables that
affect a person’s income, but are uncorrelated with the independent variable. In
addition, the cohort effect dummy variable and period effect dummy variable
should both exist in the model.
However, a self-selection issue occurs when certain unobservable variables which
also affect the binary veteran variable fail to be included in the model. Perhaps
people who would gain most benefits from military (they might obtain promises
to get high income as a veteran) choose to join the Vietnam War. Or their decision
to fight in the war is correlated with other characteristics that affect earnings.
For example, people (even from a poor family) with less IQ or ability might have
higher possibility to join the war if their parents believe they will earn more than
not being veterans. These joining-war decisions and the get-most-benefit situation
end up contained in the error term since they are hardly measurable to
be control variables. Due to the correlation with unobservable control variables,
the independent variable turns out to be endogenous. In addition, the veteran
impact on income may be overestimated since the research subjects are veterans
who have ensured higher income; or the model might underestimate the veteran
impact: Some veterans with less IQ or ability will earn even less than common
veterans because of the lacking of several-years’ education and working experience.”
教授给我的评价原文大概是：
"If you are a bad writer, people will believe you are a bad thinker--muddled words are the surest sign of muddled thoughts. You tend to add longer and more exotic words until your idea is lost and you ultimately write something that is false or unsubstantiated. It leads me to believe you want to distract rather than illuminate. "
我写的是对一篇关于IV(instrumental variable)的经济论文的review。我就摘两段自认为问题所在的段落，这两段是在说明为什么此论文的研究不能使用ols模型进行估计。如果哪位大神可以指点迷津，我不胜感激啊。
“Initially if we measure the veteran impact on income using OLS model, the
independent variable would be a binary variable: "whether the person i is a veteran
at time t in cohort c" and the dependent variable would be the person’s
income. Control variables in the model should include all the variables that
affect a person’s income, but are uncorrelated with the independent variable. In
addition, the cohort effect dummy variable and period effect dummy variable
should both exist in the model.
However, a self-selection issue occurs when certain unobservable variables which
also affect the binary veteran variable fail to be included in the model. Perhaps
people who would gain most benefits from military (they might obtain promises
to get high income as a veteran) choose to join the Vietnam War. Or their decision
to fight in the war is correlated with other characteristics that affect earnings.
For example, people (even from a poor family) with less IQ or ability might have
higher possibility to join the war if their parents believe they will earn more than
not being veterans. These joining-war decisions and the get-most-benefit situation
end up contained in the error term since they are hardly measurable to
be control variables. Due to the correlation with unobservable control variables,
the independent variable turns out to be endogenous. In addition, the veteran
impact on income may be overestimated since the research subjects are veterans
who have ensured higher income; or the model might underestimate the veteran
impact: Some veterans with less IQ or ability will earn even less than common
veterans because of the lacking of several-years’ education and working experience.”