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I analyzed all the expansions for the BGG Top 1000 Board games: A summary
#Top 20 Most Rated Expansions:
| **Expansion** | **Ratings** |
|-----------------------------------------------|:-----------:|
| Carcassonne: Expansion 1 – Inns & Cathedrals | 21210 |
| Catan: Cities & Knights | 18998 |
| Catan: Seafarers | 18325 |
| Pandemic: On the Brink | 17321 |
| Carcassonne: Expansion 2 – Traders & Builders | 16739 |
| Catan: 5-6 Player Extension | 16009 |
| Dominion: Seaside | 15412 |
| Dominion: Prosperity | 14565 |
| 7 Wonders: Leaders | 14430 |
| Terraforming Mars: Prelude | 13103 |
| Lords of Waterdeep: Scoundrels of Skullport | 12922 |
| 7 Wonders Duel: Pantheon | 12541 |
| Wingspan: European Expansion | 12119 |
| King of Tokyo: Power Up! | 11276 |
| Ticket to Ride: USA 1910 | 10731 |
| 7 Wonders: Cities | 10689 |
| Scythe: Invaders from Afar | 10304 |
| Race for the Galaxy: The Gathering Storm | 9928 |
| Terraforming Mars: Hellas & Elysium | 9749 |
| Viticulture: Tuscany Essential Edition | 8697 |
# Top 20 Highest BGG-rated Expansions:
| **Expansion** | **BGG Rating** |
|---------------------------------------------------|:---------------:|
| Terraforming Mars: Prelude | 8.39 |
| Viticulture: Tuscany Essential Edition | 8.01 |
| Scythe: The Rise of Fenris | 7.95 |
| Spirit Island: Branch & Claw | 7.95 |
| Spirit Island: Jagged Earth | 7.93 |
| Wingspan: European Expansion | 7.93 |
| Dominion: Prosperity | 7.88 |
| Terraforming Mars: Hellas & Elysium | 7.88 |
| Wingspan: Oceania Expansion | 7.84 |
| Lords of Waterdeep: Scoundrels of Skullport | 7.83 |
| Scythe: Invaders from Afar | 7.82 |
| Pandemic: On the Brink | 7.76 |
| Dominion: Seaside | 7.71 |
| Root: The Riverfolk Expansion | 7.70 |
| Dune: Imperium – Rise of Ix | 7.69 |
| Star Wars: Rebellion – Rise of the Empire | 7.68 |
| Race for the Galaxy: The Gathering Storm | 7.66 |
| Lost Ruins of Arnak: Expedition Leaders | 7.66 |
| Mage Knight Board Game: The Lost Legion Expansion | 7.63 |
| 7 Wonders Duel: Pantheon | 7.63 |
#Top 20 Expansions that "Most Improve" the Base Game
**(Based on differences in ratings for Base game and expansion, minimum 1000 ratings)**
| **Expansion** | **Delta-Rating** |
|------------------------------------------------------------------------|:----------------:|
| Space Alert: The New Frontier | 1.05 |
| Spirit Island: Jagged Earth | 1.01 |
| Sentinels of the Multiverse: Shattered Timelines | 0.96 |
| Legendary: A Marvel Deck Building Game – X-Men | 0.96 |
| Star Wars: Outer Rim – Unfinished Business | 0.92 |
| Sentinels of the Multiverse: Infernal Relics | 0.92 |
| Sid Meier's Civilization: The Board Game – Wisdom and Warfare | 0.91 |
| StarCraft: The Board Game – Brood War Expansion | 0.91 |
| Descent: Journeys in the Dark (Second Edition) – Road to Legend | 0.90 |
| Cosmic Encounter: Cosmic Dominion | 0.89 |
| Merchants & Marauders: Seas of Glory | 0.88 |
| Xia: Embers of a Forsaken Star | 0.86 |
| A Game of Thrones: The Board Game (Second Edition) – Mother of Dragons | 0.86 |
| Firefly: The Game – Kalidasa | 0.83 |
| Twilight Imperium: Third Edition – Shards of the Throne | 0.82 |
| Elder Sign: Gates of Arkham | 0.81 |
| Dominion: Empires | 0.80 |
| Legends of Andor: Journey to the North | 0.80 |
| A Feast for Odin: The Norwegians | 0.77 |
| Twilight Imperium: Third Edition – Shattered Empire | 0.76 |
#Top 20 Expansions that Most Increase the Complexity of the Base Game
**(Based on differences in Weights for Base game and expansion, minimum 1000 ratings)**
| **Expansion** | **Delta-Weight** |
|-------------------------------------------------------------------------|:-----------:|
| Isle of Skye: Journeyman | 0.72 |
| 7 Wonders Duel: Agora | 0.62 |
| Catan: Cities & Knights | 0.59 |
| Alchemists: The King's Golem | 0.59 |
| Galaxy Trucker: Another Big Expansion | 0.52 |
| Catan: Explorers & Pirates | 0.47 |
| Pandemic: In the Lab | 0.47 |
| Spirit Island: Jagged Earth | 0.46 |
| Colt Express: Marshal & Prisoners | 0.45 |
| Dominion: Nocturne | 0.45 |
| Terraforming Mars: Turmoil | 0.44 |
| Harry Potter: Hogwarts Battle – The Monster Box of Monsters Expansion | 0.44 |
| Ticket to Ride Map Collection: Volume 5 – United Kingdom & Pennsylvania | 0.42 |
| Tiny Epic Galaxies: Beyond the Black | 0.42 |
| Las Vegas Boulevard | 0.40 |
| 7 Wonders: Armada | 0.37 |
| Viticulture: Tuscany Essential Edition | 0.36 |
| Dominion: Dark Ages | 0.35 |
| Race for the Galaxy: The Brink of War | 0.35 |
| Betrayal at House on the Hill: Widow's Walk | 0.35 |
#Top 20 "Worst" Expansions
**(Based on differences in Ratings for Base game and expansion, minimum 1000 ratings)**
| **Expansion** | **Delta-Rating** |
|------------------------------------------------------------|:----------------:|
| Carcassonne: Expansion 7 – The Catapult | -2.541 |
| Ticket to Ride: Alvin & Dexter | -0.889 |
| Terraforming Mars: Turmoil | -0.838 |
| Gloomhaven: Forgotten Circles | -0.836 |
| Carcassonne: Expansion 4 – The Tower | -0.827 |
| Terraforming Mars: Venus Next | -0.818 |
| Carcassonne: King & Scout | -0.809 |
| 7 Wonders: Babel | -0.786 |
| Dominion: Alchemy | -0.672 |
| Carcassonne: Expansion 3 – The Princess & The Dragon | -0.626 |
| Carcassonne: Expansion 6 – Count, King & Robber | -0.585 |
| Star Realms: Crisis – Heroes/Events | -0.45 |
| Azul: Crystal Mosaic | -0.512 |
| Small World: Necromancer Island | -0.502 |
| Everdell: Pearlbrook | -0.408 |
| Carcassonne: Expansion 8 – Bridges, Castles and Bazaars | -0.399 |
| Puerto Rico: Expansion I – New Buildings | -0.386 |
| Scythe: The Wind Gambit | -0.349 |
| The Lord of the Rings: The Card Game – The Hunt for Gollum | -0.321 |
| Blood Rage: Gods of Ásgard | -0.289 |
#Top 20 Most Rated Expansions:
| **Expansion** | **Ratings** |
|-----------------------------------------------|:-----------:|
| Carcassonne: Expansion 1 – Inns & Cathedrals | 21210 |
| Catan: Cities & Knights | 18998 |
| Catan: Seafarers | 18325 |
| Pandemic: On the Brink | 17321 |
| Carcassonne: Expansion 2 – Traders & Builders | 16739 |
| Catan: 5-6 Player Extension | 16009 |
| Dominion: Seaside | 15412 |
| Dominion: Prosperity | 14565 |
| 7 Wonders: Leaders | 14430 |
| Terraforming Mars: Prelude | 13103 |
| Lords of Waterdeep: Scoundrels of Skullport | 12922 |
| 7 Wonders Duel: Pantheon | 12541 |
| Wingspan: European Expansion | 12119 |
| King of Tokyo: Power Up! | 11276 |
| Ticket to Ride: USA 1910 | 10731 |
| 7 Wonders: Cities | 10689 |
| Scythe: Invaders from Afar | 10304 |
| Race for the Galaxy: The Gathering Storm | 9928 |
| Terraforming Mars: Hellas & Elysium | 9749 |
| Viticulture: Tuscany Essential Edition | 8697 |
# Top 20 Highest BGG-rated Expansions:
| **Expansion** | **BGG Rating** |
|---------------------------------------------------|:---------------:|
| Terraforming Mars: Prelude | 8.39 |
| Viticulture: Tuscany Essential Edition | 8.01 |
| Scythe: The Rise of Fenris | 7.95 |
| Spirit Island: Branch & Claw | 7.95 |
| Spirit Island: Jagged Earth | 7.93 |
| Wingspan: European Expansion | 7.93 |
| Dominion: Prosperity | 7.88 |
| Terraforming Mars: Hellas & Elysium | 7.88 |
| Wingspan: Oceania Expansion | 7.84 |
| Lords of Waterdeep: Scoundrels of Skullport | 7.83 |
| Scythe: Invaders from Afar | 7.82 |
| Pandemic: On the Brink | 7.76 |
| Dominion: Seaside | 7.71 |
| Root: The Riverfolk Expansion | 7.70 |
| Dune: Imperium – Rise of Ix | 7.69 |
| Star Wars: Rebellion – Rise of the Empire | 7.68 |
| Race for the Galaxy: The Gathering Storm | 7.66 |
| Lost Ruins of Arnak: Expedition Leaders | 7.66 |
| Mage Knight Board Game: The Lost Legion Expansion | 7.63 |
| 7 Wonders Duel: Pantheon | 7.63 |
#Top 20 Expansions that "Most Improve" the Base Game
**(Based on differences in ratings for Base game and expansion, minimum 1000 ratings)**
| **Expansion** | **Delta-Rating** |
|------------------------------------------------------------------------|:----------------:|
| Space Alert: The New Frontier | 1.05 |
| Spirit Island: Jagged Earth | 1.01 |
| Sentinels of the Multiverse: Shattered Timelines | 0.96 |
| Legendary: A Marvel Deck Building Game – X-Men | 0.96 |
| Star Wars: Outer Rim – Unfinished Business | 0.92 |
| Sentinels of the Multiverse: Infernal Relics | 0.92 |
| Sid Meier's Civilization: The Board Game – Wisdom and Warfare | 0.91 |
| StarCraft: The Board Game – Brood War Expansion | 0.91 |
| Descent: Journeys in the Dark (Second Edition) – Road to Legend | 0.90 |
| Cosmic Encounter: Cosmic Dominion | 0.89 |
| Merchants & Marauders: Seas of Glory | 0.88 |
| Xia: Embers of a Forsaken Star | 0.86 |
| A Game of Thrones: The Board Game (Second Edition) – Mother of Dragons | 0.86 |
| Firefly: The Game – Kalidasa | 0.83 |
| Twilight Imperium: Third Edition – Shards of the Throne | 0.82 |
| Elder Sign: Gates of Arkham | 0.81 |
| Dominion: Empires | 0.80 |
| Legends of Andor: Journey to the North | 0.80 |
| A Feast for Odin: The Norwegians | 0.77 |
| Twilight Imperium: Third Edition – Shattered Empire | 0.76 |
#Top 20 Expansions that Most Increase the Complexity of the Base Game
**(Based on differences in Weights for Base game and expansion, minimum 1000 ratings)**
| **Expansion** | **Delta-Weight** |
|-------------------------------------------------------------------------|:-----------:|
| Isle of Skye: Journeyman | 0.72 |
| 7 Wonders Duel: Agora | 0.62 |
| Catan: Cities & Knights | 0.59 |
| Alchemists: The King's Golem | 0.59 |
| Galaxy Trucker: Another Big Expansion | 0.52 |
| Catan: Explorers & Pirates | 0.47 |
| Pandemic: In the Lab | 0.47 |
| Spirit Island: Jagged Earth | 0.46 |
| Colt Express: Marshal & Prisoners | 0.45 |
| Dominion: Nocturne | 0.45 |
| Terraforming Mars: Turmoil | 0.44 |
| Harry Potter: Hogwarts Battle – The Monster Box of Monsters Expansion | 0.44 |
| Ticket to Ride Map Collection: Volume 5 – United Kingdom & Pennsylvania | 0.42 |
| Tiny Epic Galaxies: Beyond the Black | 0.42 |
| Las Vegas Boulevard | 0.40 |
| 7 Wonders: Armada | 0.37 |
| Viticulture: Tuscany Essential Edition | 0.36 |
| Dominion: Dark Ages | 0.35 |
| Race for the Galaxy: The Brink of War | 0.35 |
| Betrayal at House on the Hill: Widow's Walk | 0.35 |
#Top 20 "Worst" Expansions
**(Based on differences in Ratings for Base game and expansion, minimum 1000 ratings)**
| **Expansion** | **Delta-Rating** |
|------------------------------------------------------------|:----------------:|
| Carcassonne: Expansion 7 – The Catapult | -2.541 |
| Ticket to Ride: Alvin & Dexter | -0.889 |
| Terraforming Mars: Turmoil | -0.838 |
| Gloomhaven: Forgotten Circles | -0.836 |
| Carcassonne: Expansion 4 – The Tower | -0.827 |
| Terraforming Mars: Venus Next | -0.818 |
| Carcassonne: King & Scout | -0.809 |
| 7 Wonders: Babel | -0.786 |
| Dominion: Alchemy | -0.672 |
| Carcassonne: Expansion 3 – The Princess & The Dragon | -0.626 |
| Carcassonne: Expansion 6 – Count, King & Robber | -0.585 |
| Star Realms: Crisis – Heroes/Events | -0.45 |
| Azul: Crystal Mosaic | -0.512 |
| Small World: Necromancer Island | -0.502 |
| Everdell: Pearlbrook | -0.408 |
| Carcassonne: Expansion 8 – Bridges, Castles and Bazaars | -0.399 |
| Puerto Rico: Expansion I – New Buildings | -0.386 |
| Scythe: The Wind Gambit | -0.349 |
| The Lord of the Rings: The Card Game – The Hunt for Gollum | -0.321 |
| Blood Rage: Gods of Ásgard | -0.289 |
| 33,000 mlx | |
| 40 | |
| 4 |