Questions for Thought

These questions consider stock in Pfizer, the pharmaceutical manufacturer. The data are monthly and span 1944 through November 2015.

  1. The timeplot in Figure 9 shows the price at the end of the month of one share of stock in Pfizer. What seems to be happening? How could you verify your answer?

    A timeplot

    Figure 9 Timeplot of the price of stock in Pfizer.

  2. Figure 10 tracks the value of an initial $100 investment made in Pfizer in 1944. For each month, the value given is the amount invested in Pfizer at the end of the previous month multiplied by the percentage change during the month. The value of the ...

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