主题：【讨论】运十, 高铁, 和汽车工业 -- 大漠孤烟远

小虎和鼎革一再强调引入对数不是为了计算方便。经济和数学是两个学科等等，其实只是利用自己的专业身份向观众暗示：我没有错，我说的是经济学，他是野狐禅。

可是wikipedia已经说得很清楚：

The above relation gives a very simplified picture of the economy in a single year; what growth theory econometrics does is to look at a sequence of years to find a statistically significant pattern in the changes of the variables, and perhaps identify the existence and value of the "Solow residual". The most basic technique for doing this is to assume constant rates of change in all the variables (obscured by noise), and regress on the data to find the best estimate of these rates in the historical data available (using an Ordinary least squares regression). Economists always do this by first taking the natural log of their equation (to separate out the variables on the right-hand-side of the equation); logging both sides of this production function produces a simple linear regression with an error term,

http://en.wikipedia.org/wiki/Solow_residual

这说得很清楚，取对数是为了分离变量，获得简单的线性回归方程，以方便计算，而根本没有任何他们所暗示的特殊的，神秘的经济学意义。