RuneScape:Grand Exchange Market Watch/Adjustments (29 September 2012)

The Discontinued Rare Index (DRI) was adjusted on 29 September 2012. The following templates were affected: Template:GE Discontinued Rare Index and Template:GE Discontinued Rare Index/Diff.

One item was added: Fish mask. This brought the total of items in the DRI from 15 to 16 items.

From the old divisor obtained from the templates:


 * $${div}_{\text{old}} = 15$$

We need to calculate a new divisor:


 * $${div}_{\text{new}} = {div}_{\text{old}} \times \frac{\sum \left ( \frac{p}{q} \right )_{\text{new}}}{\sum \left ( \frac{p}{q} \right )_{\text{old}}}$$

To calculate the new divisor, we need to find:


 * $$\begin{align}

\sum \left ( \frac{p}{q} \right )_{\text{old}} & = \text{sum of ratios prior to change} \\

& = \frac{2,146,908,554}{688,800,000} + \frac{2,147,483,647}{340,100,000} + \frac{1,124,859,082}{114,800,000} + \dots + \frac{261,000,577}{31,100,000} \\

& = 181.52107486 \text{ (up to 8 d.p.)}

\end{align}$$

And also:


 * $$\begin{align}

\sum \left ( \frac{p}{q} \right )_{\text{new}} & = \text{sum of ratios prior to change} - \text{sum of removed ratios} + \text{sum of added ratios} \\

& = \sum \left ( \frac{p}{q} \right )_{\text{old}} - \text{sum of removed ratios} + \text{number of added items} \\

& = 181.52107486 - 0 + 1 \\

& = 182.52107486 \text{ (up to 8 d.p.)}

\end{align}$$

Thus, the new divisor is:


 * $$\begin{align}

{div}_{\text{new}} & = {div}_{\text{old}} \times \frac{\sum \left ( \frac{p}{q} \right )_{\text{new}}}{\sum \left ( \frac{p}{q} \right )_{\text{old}}} \\

& = 15 \times \frac{182.52107486}{181.52107486} \\

& = 15.0826 \text{ (4 d.p.)}

\end{align}$$