Indices must be adapted constantly to changing conditions so they can fulfill their purpose as measuring instruments for the Grand Exchange Market Watch. Price and volume data must also be adjusted on occasions where there is missing data, data vandalism in the wiki, or when the official Grand Exchange Database produces incomplete or erroneous data.

This page lists the methods and calculations used for the adjustments made to the indices and the data. For general information regarding the Grand Exchange Market Watch, see Grand Exchange Market Watch/FAQ.

## Indices

### 2008

10 January 2008
Coal ca. December 2007 159 Unknown Unchanged
Steel bar 540
Gold ore 528
Nature rune 271
Death rune 299
Pure essence 80
Yew logs 411
Magic logs 1,222
Cowhide 109
Flax 70
Soft clay 207
Limpwurt root 646
Law rune 303
Big bones 419
Raw lobster 237
Raw swordfish 237
Raw monkfish 350
Snape grass 428
Clean ranarr 5,959
Clean kwuarm 3,030
Clean snapdragon 6,885
Vial of water 98

### 2011

14 October 2011
Air rune 15 December 2007 11 6 Unchanged
Mind rune 10 3
Water rune 15 6
Earth rune 11 13
Fire rune 10 4
Body rune 9 5
Cosmic rune 140 107
Chaos rune 102 38
Nature rune 258 100
Law rune 304 158
Death rune 299 181
Astral rune 132 81
Blood rune 336 211
Soul rune 335 556

Calculations

From the old divisor obtained from the templates:

${div}_{\text{old}}=14.0000$ 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{aligned}\sum \left({\frac {p}{q}}\right)_{\text{old}}&={\text{sum of ratios prior to change}}\\&={\frac {6}{11}}+{\frac {3}{10}}+{\frac {6}{15}}+\dots +{\frac {556}{335}}\\&=8.93366198{\text{ (up to 8 d.p.)}}\end{aligned}} And also:

{\begin{aligned}\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}}\\&=8.93366198-0+1\\&=9.933661982{\text{ (up to 8 d.p.)}}\end{aligned}} Thus, the new divisor is:

{\begin{aligned}{div}_{\text{new}}&={div}_{\text{old}}\times {\frac {\sum \left({\frac {p}{q}}\right)_{\text{new}}}{\sum \left({\frac {p}{q}}\right)_{\text{old}}}}\\&=14.0000\times {\frac {9.93366198}{8.93366198}}\\&=15.5671{\text{ (4 d.p.)}}\end{aligned}} 6 November 2011
Grimy guam 9 June 2009 490 121 Unchanged
Grimy marrentill 192 25
Grimy tarromin 216 121
Grimy harralander 787 100
Grimy ranarr 7,654 4,032
Grimy irit 1,552 1,172
Grimy wergali 1,800 2,450
Grimy spirit weed 1,917 2,658
Grimy avantoe 1,591 3,293
Grimy kwuarm 2,850 1,356
Grimy snapdragon 9,720 5,224
Grimy dwarf weed 2,042 4,744
Grimy torstol 2,980 25,300
Clean guam 481 126
Clean marrentill 101 16
Clean tarromin 193 143
Clean harralander 791 100
Clean ranarr 7,719 3,867
Clean irit 1,795 1,232
Clean wergali 2,000 2,331
Clean spirit weed 1,888 2,725
Clean avantoe 1,593 3,253
Clean kwuarm 2,881 1,389
Clean snapdragon 9,726 5,402
Clean dwarf weed 2,070 4,668
Clean torstol 2,762 25,400
Clean fellstalk 1,437

Calculations

From the old divisor obtained from the templates:

${div}_{\text{old}}=32.0000$ 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{aligned}\sum \left({\frac {p}{q}}\right)_{\text{old}}&={\text{sum of ratios prior to change}}\\&={\frac {121}{490}}+{\frac {25}{192}}+{\frac {121}{216}}+\dots +{\frac {25,400}{2,762}}\\&=51.57722802{\text{ (up to 8 d.p.)}}\end{aligned}} And also:

{\begin{aligned}\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}}\\&=51.57722802-0+2\\&=53.57722802{\text{ (up to 8 d.p.)}}\end{aligned}} Thus, the new divisor is:

{\begin{aligned}{div}_{\text{new}}&={div}_{\text{old}}\times {\frac {\sum \left({\frac {p}{q}}\right)_{\text{new}}}{\sum \left({\frac {p}{q}}\right)_{\text{old}}}}\\&=32.0000\times {\frac {53.57722802}{51.57722802}}\\&=33.2409{\text{ (4 d.p.)}}\end{aligned}} ### 2012

12 February 2012
Coal ca. December 2007 159 320 Unchanged
Steel bar 540 1,335
Gold ore 528 304
Nature rune 271 226
Death rune 299 452
Pure essence 80 125
Yew logs 411 522
Magic logs 1,222 1,592
Cowhide 109 513
Flax 70 72
Soft clay 207 541
Limpwurt root 646 2,060
Raw lobster 237 285
Raw monkfish 10 January 2008 350 601
Snape grass 428 314
Clean snapdragon 6,885 9,866
Clean kwuarm 3,030 1,828
Law rune ca. December 2007 303 363 Removed item
Big bones 419 621
Raw swordfish 10 January 2008 325 492
Mithril ore 315 349
Vial of water 98 36
Clean ranarr 5,959 4,958
Dragon boots 103,701
Rune armour set (lg) 136,531
Red chinchompa 1,592
Oak plank 639
Shark 1,715
Green dragonhide 2,196
Dragon bones 3,962
Cannonball 407
Dragonfire shield 7,946,801

Calculations

From the old divisor obtained from the templates:

${div}_{\text{old}}=21.791759207424$ 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{aligned}\sum \left({\frac {p}{q}}\right)_{\text{old}}&={\text{sum of ratios prior to change}}\\&=\left({\frac {320}{159}}+{\frac {1,335}{540}}+\dots +{\frac {1,828}{3,030}}\right)+\left({\frac {363}{303}}+{\frac {621}{419}}+\dots +{\frac {4,958}{5,959}}\right)\\&=35.26980062{\text{ (up to 8 d.p.)}}\end{aligned}} And also:

{\begin{aligned}\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}}\\&=35.26980062-\left({\frac {363}{303}}+{\frac {621}{419}}+\dots +{\frac {4,958}{5,959}}\right)+10\\&=38.76853218{\text{ (up to 8 d.p.)}}\end{aligned}} Thus, the new divisor is:

{\begin{aligned}{div}_{\text{new}}&={div}_{\text{old}}\times {\frac {\sum \left({\frac {p}{q}}\right)_{\text{new}}}{\sum \left({\frac {p}{q}}\right)_{\text{old}}}}\\&=21.791759207424\times {\frac {38.76853218}{35.26980062}}\\&=23.9535{\text{ (4 d.p.)}}\end{aligned}} 29 September 2012
Christmas cracker 31 December 2008 688,800,000 2,146,908,554 Unchanged
Blue partyhat 340,100,000 2,147,483,647
Green partyhat 114,800,000 1,124,859,082
Purple partyhat 83,100,000 895,254,988
Red partyhat 129,400,000 1,232,179,013
White partyhat 183,300,000 1,652,939,303
Yellow partyhat 96,300,000 948,567,763
Pumpkin 5,300,000 165,935,075
Easter egg 4,300,000 56,837,419
Santa hat 14,800,000 116,884,816
Disk of returning 4,700,000 171,076,782
Half full wine jug 31,100,000 261,000,577

Calculations

From the old divisor obtained from the templates:

${div}_{\text{old}}=15.0000$ 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{aligned}\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{aligned}} And also:

{\begin{aligned}\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{aligned}} Thus, the new divisor is:

{\begin{aligned}{div}_{\text{new}}&={div}_{\text{old}}\times {\frac {\sum \left({\frac {p}{q}}\right)_{\text{new}}}{\sum \left({\frac {p}{q}}\right)_{\text{old}}}}\\&=15.0000\times {\frac {182.52107486}{181.52107486}}\\&=15.0826{\text{ (4 d.p.)}}\end{aligned}} ### 2013

20 January 2013
Christmas cracker 31 December 2008 688,800,000 2,147,476,523 Unchanged
Blue partyhat 340,100,000 2,147,483,647
Green partyhat 114,800,000 1,439,919,758
Purple partyhat 83,100,000 1,194,593,128
Red partyhat 129,400,000 1,588,813,583
White partyhat 183,300,000 2,115,586,339
Yellow partyhat 96,300,000 1,288,308,900
Pumpkin 5,300,000 153,543,323
Easter egg 4,300,000 73,851,614
Santa hat 14,800,000 130,038,816
Disk of returning 4,700,000 193,631,082
Half full wine jug 31,100,000 282,814,298
Fish mask 29 September 2012 4,555,462 1,778,504
Christmas tree hat 2,295,576 Added item

Calculations

From the old divisor obtained from the templates:

${div}_{\text{old}}=15.0826$ 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{aligned}\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 {1,439,919,758}{114,800,000}}+\dots +{\frac {1,778,504}{4,555,462}}\\&=209.14534690{\text{ (up to 8 d.p.)}}\end{aligned}} And also:

{\begin{aligned}\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}}\\&=209.14534690-0+1\\&=210.14534690{\text{ (up to 8 d.p.)}}\end{aligned}} Thus, the new divisor is:

{\begin{aligned}{div}_{\text{new}}&={div}_{\text{old}}\times {\frac {\sum \left({\frac {p}{q}}\right)_{\text{new}}}{\sum \left({\frac {p}{q}}\right)_{\text{old}}}}\\&=15.0826\times {\frac {210.14534690}{209.14534690}}\\&=15.1547{\text{ (4 d.p.)}}\end{aligned}} 23 July 2013
Christmas cracker 31 December 2008 688,800,000 2,147,483,557 Unchanged
Blue partyhat 340,100,000 2,147,483,647
Green partyhat 114,800,000 1,845,813,270
Purple partyhat 83,100,000 1,514,338,96
Red partyhat 129,400,000 2,100,264,784
White partyhat 183,300,000 2,147,483,598
Yellow partyhat 96,300,000 1,607,195,89
Pumpkin 5,300,000 177,606,966
Easter egg 4,300,000 82,884,794
Santa hat 14,800,000 149,818,733
Disk of returning 4,700,000 226,927,013
Half full wine jug 31,100,000 320,604,356
Fish mask 29 September 2012 4,555,462 1,446,274
Christmas tree hat 20 January 2013 2,295,576 26,024,637
Crown of Seasons 8,307,542 Added item

Calculations

From the old divisor obtained from the templates:

${div}_{\text{old}}=15.1547$ 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{aligned}\sum \left({\frac {p}{q}}\right)_{\text{old}}&={\text{sum of ratios prior to change}}\\&={\frac {2,147,483,557}{688,800,000}}+{\frac {2,147,483,647}{340,100,000}}+{\frac {1,845,813,270}{114,800,000}}+\dots +{\frac {26,024,637}{2,295,576}}\\&=260.57227963{\text{ (up to 8 d.p.)}}\end{aligned}} And also:

{\begin{aligned}\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}}\\&=260.57227963-0+1\\&=261.57227963{\text{ (up to 8 d.p.)}}\end{aligned}} Thus, the new divisor is:

{\begin{aligned}{div}_{\text{new}}&={div}_{\text{old}}\times {\frac {\sum \left({\frac {p}{q}}\right)_{\text{new}}}{\sum \left({\frac {p}{q}}\right)_{\text{old}}}}\\&=15.1547\times {\frac {261.57227963}{260.57227963}}\\&=15.2129{\text{ (4 d.p.)}}\end{aligned}} 8 November 2013
Logs 19 December 2007 34 28 Unchanged
Achey tree logs 40 39
Oak logs 18 12
Willow logs 22 20
Teak logs 136 71
Maple logs 46 30
Mahogany logs 173 392
Arctic pine logs 855 57
Yew logs 413 526
Magic logs 1,221 1,646

Calculations

From the old divisor obtained from the templates:

${div}_{\text{old}}=10.0000$ 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{aligned}\sum \left({\frac {p}{q}}\right)_{\text{old}}&={\text{sum of ratios prior to change}}\\&={\frac {280}{34}}+{\frac {399}{40}}+{\frac {123}{18}}+\dots +{\frac {1,646}{1,221}}\\&=32.08119681{\text{ (up to 8 d.p.)}}\end{aligned}} And also:

{\begin{aligned}\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}}\\&=32.08119681-0+1\\&=33.08119681{\text{ (up to 8 d.p.)}}\end{aligned}} Thus, the new divisor is:

{\begin{aligned}{div}_{\text{new}}&={div}_{\text{old}}\times {\frac {\sum \left({\frac {p}{q}}\right)_{\text{new}}}{\sum \left({\frac {p}{q}}\right)_{\text{old}}}}\\&=10.0000\times {\frac {33.08119681}{32.08119681}}\\&=10.3117{\text{ (4 d.p.)}}\end{aligned}} ### 2014

20 January 2014
Christmas cracker 31 December 2008 688,800,000 2,147,483,632 Unchanged
Blue partyhat 340,100,000 2,147,483,647
Green partyhat 114,800,000 1,490,829,327
Purple partyhat 83,100,000 1,279,369,134
Red partyhat 129,400,000 1,696,893,747
White partyhat 183,300,000 2,146,833,194
Yellow partyhat 96,300,000 1,335,202,311
Pumpkin 5,300,000 174,290,712
Easter egg 4,300,000 70,272,905
Santa hat 14,800,000 135,913,306
Disk of returning 4,700,000 223,384,911
Half full wine jug 31,100,000 333,709,743
Fish mask 29 September 2012 4,555,462 944,822
Christmas tree hat 20 January 2013 2,295,576 12,593,302
Crown of Seasons 23 July 2013 8,307,542 3,926,892
Black Santa hat 222,967,707 Added item

Calculations

From the old divisor obtained from the templates:

${div}_{\text{old}}=15.2129$ 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{aligned}\sum \left({\frac {p}{q}}\right)_{\text{old}}&={\text{sum of ratios prior to change}}\\&={\frac {2,147,483,557}{688,800,000}}+{\frac {2,147,483,647}{340,100,000}}+{\frac {1,490,829,327}{114,800,000}}+\dots +{\frac {12,593,302}{2,295,576}}+{\frac {3,926,892}{8,307,542}}\\&=230.87579845{\text{ (up to 8 d.p.)}}\end{aligned}} And also:

{\begin{aligned}\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}}\\&=230.87579845-0+1\\&=231.87579845{\text{ (up to 8 d.p.)}}\end{aligned}} Thus, the new divisor is:

{\begin{aligned}{div}_{\text{new}}&={div}_{\text{old}}\times {\frac {\sum \left({\frac {p}{q}}\right)_{\text{new}}}{\sum \left({\frac {p}{q}}\right)_{\text{old}}}}\\&=15.2129\times {\frac {231.87579845}{230.87579845}}\\&=15.2787{\text{ (4 d.p.)}}\end{aligned}} 19 June 2014
Christmas cracker 31 December 2008 688,800,000 2,147,483,644 Unchanged
Blue partyhat 340,100,000 2,147,483,647
Green partyhat 114,800,000 1,512,978,741
Purple partyhat 83,100,000 1,242,748,792
Red partyhat 129,400,000 1,706,390,538
White partyhat 183,300,000 2,147,481,758
Yellow partyhat 96,300,000 1,325,097,236
Pumpkin 5,300,000 157,608,053
Easter egg 4,300,000 62,666,643
Santa hat 14,800,000 125,533,632
Disk of returning 4,700,000 211,466,440
Half full wine jug 31,100,000 348,603,157
Fish mask 29 September 2012 4,555,462 669,574
Christmas tree hat 20 January 2013 2,295,576 12,559,556
Crown of Seasons 23 July 2013 8,307,542 4,555,009
Black Santa hat 20 January 2013 222,967,707 410,924,805
Cloak of Seasons 7,614,236 Added item

Calculations

From the old divisor obtained from the templates:

${div}_{\text{old}}=15.2787$ 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{aligned}\sum \left({\frac {p}{q}}\right)_{\text{old}}&={\text{sum of ratios prior to change}}\\&={\frac {2,147,483,644}{688,800,000}}+{\frac {2,147,483,647}{340,100,000}}+{\frac {1,512,978,741}{114,800,000}}+\dots +{\frac {4,555,009}{8,307,542}}+{\frac {410,924,805}{222,967,707}}\\&=221.84047459{\text{ (up to 8 d.p.)}}\end{aligned}} And also:

{\begin{aligned}\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}}\\&=221.84047459-0+1\\&=222.84047459{\text{ (up to 8 d.p.)}}\end{aligned}} Thus, the new divisor is:

{\begin{aligned}{div}_{\text{new}}&={div}_{\text{old}}\times {\frac {\sum \left({\frac {p}{q}}\right)_{\text{new}}}{\sum \left({\frac {p}{q}}\right)_{\text{old}}}}\\&=15.2787\times {\frac {222.84047459}{221.84047459}}\\&=15.3476{\text{ (4 d.p.)}}\end{aligned}} 30 August 2014
Air rune 15 December 2007 11 19 Unchanged
Mind rune 10 6
Water rune 15 26
Earth rune 11 14
Fire rune 10 22
Body rune 9 8
Cosmic rune 140 245
Chaos rune 102 41
Nature rune 258 263
Law rune 304 281
Death rune 299 163
Astral rune 132 245
Blood rune 336 261
Soul rune 335 153
Armadyl rune 14 October 2011 1,817 389
Mist rune 348
Dust rune 66
Smoke rune 314
Mud rune 775
Lava rune 49

Calculations

From the old divisor obtained from the templates:

${div}_{\text{old}}=15.5671$ 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{aligned}\sum \left({\frac {p}{q}}\right)_{\text{old}}&={\text{sum of ratios prior to change}}\\&={\frac {19}{11}}+{\frac {6}{10}}+{\frac {26}{15}}+\dots +{\frac {153}{335}}+{\frac {389}{1,817}}\\&=16.36670735{\text{ (up to 8 d.p.)}}\end{aligned}} And also:

{\begin{aligned}\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}}\\&=16.36670735-0+6\\&=22.36670735{\text{ (up to 8 d.p.)}}\end{aligned}} Thus, the new divisor is:

{\begin{aligned}{div}_{\text{new}}&={div}_{\text{old}}\times {\frac {\sum \left({\frac {p}{q}}\right)_{\text{new}}}{\sum \left({\frac {p}{q}}\right)_{\text{old}}}}\\&=15.5671\times {\frac {22.36670735}{16.36670735}}\\&=21.2740{\text{ (4 d.p.)}}\end{aligned}} 30 December 2014
Christmas cracker 31 December 2008 688,800,000 2,147,483,644 Unchanged
Blue partyhat 340,100,000 2,147,483,647
Green partyhat 114,800,000 1,452,340,733
Purple partyhat 83,100,000 1,233,390,908
Red partyhat 129,400,000 1,738,594,833
White partyhat 183,300,000 2,147,483,644
Yellow partyhat 96,300,000 1,314,553,072
Pumpkin 5,300,000 149,804,919
Easter egg 4,300,000 49,183,614
Santa hat 14,800,000 115,823,577
Disk of returning 4,700,000 200,971,362
Half full wine jug 31,100,000 348,603,157
Fish mask 29 September 2012 4,555,462 601,926
Christmas tree hat 20 January 2013 2,295,576 12,651,188
Crown of Seasons 23 July 2013 8,307,542 4,044,842
Black Santa hat 20 January 2013 222,967,707 340,890,058
Cloak of Seasons 19 June 2014 7,614,236 27,631,528
Off-hand rubber turkey 3,590,829
Christmas scythe 72,191,580
Holly wreath 372,492,991

Calculations

From the old divisor obtained from the templates:

${div}_{\text{old}}=15.3476$ 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{aligned}\sum \left({\frac {p}{q}}\right)_{\text{old}}&={\text{sum of ratios prior to change}}\\&={\frac {2,147,483,644}{688,800,000}}+{\frac {2,147,483,647}{340,100,000}}+{\frac {1,452,340,733}{114,800,000}}+\dots +{\frac {340,890,058}{222,967,707}}+{\frac {27,631,528}{7,614,236}}\\&=211.91329563{\text{ (up to 8 d.p.)}}\end{aligned}} And also:

{\begin{aligned}\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}}\\&=211.91329563-0+4\\&=215.91329563{\text{ (up to 8 d.p.)}}\end{aligned}} Thus, the new divisor is:

{\begin{aligned}{div}_{\text{new}}&={div}_{\text{old}}\times {\frac {\sum \left({\frac {p}{q}}\right)_{\text{new}}}{\sum \left({\frac {p}{q}}\right)_{\text{old}}}}\\&=15.3476\times {\frac {215.91329563}{211.91329563}}\\&=15.6373{\text{ (4 d.p.)}}\end{aligned}} ### 2015

20 May 2015
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
Wild pie 3,491 985
Redberry pie 381 1,280
Garden pie 657 475
Stew 100 1,102
Strawberries (5) 318
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{aligned}\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{aligned}} And also:

{\begin{aligned}\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{aligned}} Thus, the new divisor is:

{\begin{aligned}{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{aligned}} ## Price data

Price updating prior to 2012 was done by users either by: checking the in-game prices, or by referring to the Grand Exchange Database. The price data, however, were neither 100% accurate (due to rounding and human errors), nor continuous (due to lack of source for historical data). However, in 2012, Jagex started storing accurate historical data in their database for up to 180 days. This enabled our bots (and users) to obtain continuous accurate data.

Nevertheless, there have been several occasions where the Grand Exchange Database failed:

23–26 March 2012
• Update: Unknown (edit)
• Affected period: 23–26 March 2012 (4 days)
• Affected items: All items
• Comment: Prices from 22 March 2012 shown throughout the affected period.

To approximate the prices, the average of the closest known prices (22 March and 27 March) is used. The formula for the k-th missing price is as follows:

${p}_{\text{k}}={p}_{\text{start}}+{\frac {{p}_{\text{end}}-{p}_{\text{start}}}{({d}_{{\text{end}}\to {\text{start}}})}}\times ({d}_{{\text{k}}\to {\text{start}}})$ For example, if the price for Item A is 331 coins on 22 March (P22) and 292 coins on 27 March (P27), then the price for 23 March (P23) would be:

{\begin{aligned}{p}_{\text{23}}&={p}_{\text{22}}+{\frac {{p}_{\text{27}}-{p}_{\text{22}}}{({d}_{{\text{27}}\to {\text{22}}})}}\times ({d}_{{\text{23}}\to {\text{22}}})\\\\&=331+{\frac {292-331}{5}}\times 1\\\\&=323.2=323\;{\text{(rounded to nearest coin)}}\end{aligned}} And, the price for 24 March (P24) would be:

{\begin{aligned}{p}_{\text{24}}&={p}_{\text{22}}+{\frac {{p}_{\text{27}}-{p}_{\text{22}}}{({d}_{{\text{27}}\to {\text{22}}})}}\times ({d}_{{\text{24}}\to {\text{22}}})\\\\&=331+{\frac {292-331}{5}}\times 2\\\\&=315.4=315\;{\text{(rounded to nearest coin)}}\end{aligned}} And so on. Thus, using the formula for the missing days, the approximate prices would be:

Date > 22 March 23 March 24 March 25 March 26 March 27 March
Item A (price) 331
(actual)
323
(calculated)
315
(calculated)
308
(calculated)
300
(calculated)
292
(actual)
6–12 November 2012
• Update: Tears of Guthix: Go with the Flow
• Affected period: 6–12 November 2012 (7 days)
• Affected items: All items
• Comment: Prices from 5 November 2012 shown throughout the affected period.
3–8 April 2013
17–21 July 2013
• Update: Open Beta Update
• Affected period: 17–21 July 2013 (5 days)
• Affected items: All items
• Comment: Prices from 16 July 2013 shown throughout the affected period. On 22 July 2013, Grand Exchange was taken offline for several hours.
8–14 October 2013
• Update: Treevolution - High-Level Trees
• Affected period: 8–14 October 2013 (7 days)
• Affected items: All items, including 10 new items added during update
• Comment: All items had prices shown from 7 October 2013. Prices for 10 new items shown as zero throughout affected period.
26 November – 1 December 2013
• Update: Coinshare, World Map and Tutorial
• Affected period: 26 November – 1 December 2013 (6 days)
• Affected items: All items, including 60 new items added during update
• Comment: Prices from 25 November 2013 shown throughout the affected period. Manual updating by users was also used to obtain in-game prices.