RuneScape:Grand Exchange Market Watch/Adjustments (20 May 2015)

20 May 2015

Adjusted index: Food Index Adjustment date: 20 May 2015 Affected templates: Template:GE Food Index and Template:GE Food Index/Diff Added item(s): 7 — Bread, Cavefish, Great white shark, Rocktail, Salmon, Saradomin brew (4), Strawberries (5) Removed item(s): 11 — Admiral pie, Garden pie, Kebab, Manta ray, Redberry pie, Roast bird meat, Sea turtle, Stew, Sweetcorn, Ugthanki kebab, Wild pie Items before adjustment: 19 Items after adjustment: 15 Divisor before adjustment: 19.0000 Divisor after adjustment: 8.7619 Item Base date Base price Price on adjustment date Comments Lobster 25 January 2008 175 196 Unchanged Bass 195 225 Tuna 81 163 Swordfish 272 295 Monkfish 233 336 Shark 657 739 Cake 52 91 Chocolate cake 150 421 Ugthanki kebab 887 810 Removed item Kebab 32 276 Sea turtle 1,264 2,690 Manta ray 1,794 1,907 Sweetcorn 135 43 Roast bird meat 22 19 Admiral pie 1,031 497 Wild pie 3,491 985 Redberry pie 381 1,280 Garden pie 657 475 Stew 100 1,102 Bread – – 433 Added item Strawberries (5) 318 Saradomin brew (4) 9,762 Salmon 80 Cavefish 1,256 Rocktail 1,814 Great white shark 912 Calculations From the old divisor obtained from the templates: ${div}_{\text{old}} = 19.0000$ 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: $\begin{align} \sum \left ( \frac{p}{q} \right )_{\text{old}} & = \text{sum of ratios prior to change} \\ & = \text{sum of unchanged ratios} + \text{sum of removed ratios} \\ & = \left (\frac{196}{175} + \frac{225}{195} + \dots + \frac{421}{150} \right ) + \left (\frac{810}{887} + \frac{276}{32} + \dots + \frac{1,102}{100} \right ) \\ & = 42.27255853 \text{ (up to 8 d.p.)} \end{align}$ And also: $\begin{align} \sum \left ( \frac{p}{q} \right )_{\text{new}} & = \text{sum of ratios prior to change} - \text{sum of removed ratios} + \text{sum of added ratios} \\ & = \sum \left ( \frac{p}{q} \right )_{\text{old}} - \text{sum of removed ratios} + \text{number of added items} \\ & = 42.27255853 - \left ( \frac{810}{887} + \frac{276}{32} + \dots + \frac{1,102}{100} \right ) + 7 \\ & = 19.49428715 \text{ (up to 8 d.p.)} \end{align}$ Thus, the new divisor is: $\begin{align} {div}_{\text{new}} & = {div}_{\text{old}} \times \frac{\sum \left ( \frac{p}{q} \right )_{\text{new}}}{\sum \left ( \frac{p}{q} \right )_{\text{old}}} \\ & = 19.0000 \times \frac{42.27255853}{19.49428715} \\ & = 8.7619 \text{ (4 d.p.)} \end{align}$