问题如下：
Zimt AG wrote down the value of its inventory in 2007 and reversed the write-down in 2008. Compared to the results the company would have reported if the write-down had never occurred, Zimt’s reported 2008:(assume the companies use a periodic inventory system)
选项：
A.profit was overstated.
B.cash flow from operations was overstated.
C.year-end inventory balance was overstated.
解释：
A is correct.
The reversal of the write-down shifted cost of sales from 2008 to 2007. The 2007 cost of sales was higher because of the write-down, and the 2008 cost of sales was lower because of the reversal of the write-down. As a result, the reported 2008 profits were overstated. Inventory balance in 2008 is the same because the write-down and reversal cancel each other out. Cash flow from operations is not affected by the non-cash write-down, but the higher profits in 2008 likely resulted in higher taxes and thus lower cash flow from operations.
题目问相比假设不发生减值&回转的话2008年的财报上的数字，真实的2008年财报数字会怎么样？
相比没发生减值&回转的情形，实际的2008年的COGS降低，因此NI增加，所以profit高估了，选项A正确。
减值和回转不影响现金流，但是影响到应税所得，所以利润高的情况下交税多，CFO就少，真实情况的2008年利润高，所以CFO低，而不是overstated，选项B错误。
真实情况是发生了存货跌价，但是又转回了，存货价值先降低，然后又增加，最后的存货价值与没发生减值&回转的情况是相同的，所两种情况下，2008年存货的价值是相等的，不存在高估或低估的情况，选项C错误。
为什么write-down会导致 COGS 上升呢？
