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} $

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