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  1. #1
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    Growth Percentage

    Hi, I was hoping someone can help me solve this conundrum. I have a chart of crude steel production per month and which also shows production growth. I would really like to know how this growth percentage has been calculated.
    Crude Steel Prod.jpg
    Rgds
    Mike

  2. #2
    WS Lounge VIP sdckapr's Avatar
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    Not sure exactly what your question is. If you are asking about the "Poly. (Global Production Growth)" , It is tough to tell exactly from your screen shot, but I would speculate that the "Poly. (Global Production Growth)" was created as a trendline to the "Global Production Growth" line as "polynomial". It appears to be a polyol of order 2, so it would have used the raw X,Y data points to create an equation of the form:
    y= A0 + A1x + A2x

    Internally the program uses a linear regression method to find the values of A0,A1, and A2 so that the resulting equation minimizes the square of the deviation from the observed Y value at each X to the calc Y at that X. The methodology typically involves matrix math [see for example http://en.wikipedia.org/wiki/Regression_analysis]

    If you are asking something else, could you elaborate?

    Steve

  3. #3
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    Hi Steve, thanks for your reply. You must be Steve Austin because that answer is coming from a bionic brain and you answered my next question before i asked it.
    I managed to finally figure out that the growth line is calculated on a y-o-y basis, rather than a mth-o-mth basis, and then your answer helps solve the rest.
    Many thanks
    Mike

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