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# 80 percentile openings

Sep 11, 2011, 8:45 AM 1

In an attempt to get a hold on all the openings out there, I've decided to begin be looking at the most common openings first, move by move. More specifically, I will systematically look at the 80 percentile reply to every move.

The most common first move is 1. e4. This is called King's Pawn (B00), and is - according to Chess.com's Master Games Database played in 46 % of all games. The second most common first move is 1. d4. It's called the Queen Pawn Opening (A40), and is played in 35 % of all master games. Together these two first moves are played in 81 % of all games, above the 80 % threshold, and so, we will simply neglect the remaining 18 first moves, since they are played so rarely. By knowing the main lines for 1. e4 and 1. d4, we will know what to expect in most of the games we'll ever play.

Replies to 1. e4

Most common is 1...c5, the Sicilian Defense (B20), played as the reply to 1. e4 in 46 % of all master games. Second is 1...e5, the King Pawn Game (C20), played in 22 % of the games in the database. Third is 1...e6, the French Defense (C00), the reply to 1. e4 in 13 % of the games. Together these three moves account for 80 % of all replies to 1. e4, so we will only consider these.

Replies to 1. d4

We needed three replies to 1. e4 to pass the 80 percentile threshold, but we'll need to remember only two replies to 1. d4. First, 1...Nf6, the Indian Game (A45), played in no less than 61 % of all games in the database as a reply to 1. d4. Secondly, 1...d5, the Queen Pawn Game (24 %). So, in 85 % of all games beginning with 1. d4, we can expect one of these two replies.

So far, so good. We now know the five most common string of moves for White and Black. Next, we'll look at the 80 percentile reply for White to all of them, one by one.

Reply to 1. e4 c5, the Sicilian Defense

This one is easy, since one move accounts for 80 % of all replies, with the second most common used in only 8 % of all master games. The move is 2. Nf3, labeled Sicilian Defense: Misc, Defenses (B27)

Reply to 1. e4 e5, the King Pawn Game

Another easy one, used in 88 % of all games in the database. The reply is the same as the previous one, namely 2. Nf3. It's called the King's Knight Opening (C40)

Reply to 1. e4 e6, the French Defense

Again, only one move to remember, the reply in 87 % of French Defense games. The move is 2. d4, and it's called French Defense: Normal Variation (C00)

Replies to 1. d4 Nf6, the Indian Game

This time there are two moves to remember. The most common is 2. c4, the Indian Game: Normal Variation (A50), used in 70 % of all master games. The second is 2. Nf3, the Indian Game: Knights Variation (A46), played in 25 % of the games. In sum, these two replies account for 94 % of all replies to 1. d4 Nf6

Replies to 1. d4 d5, the Queen Pawn Game

Again there are two moves to remember, and they are exactly the same as the previous two replies, namely 2. c4 and 2. Nf3. The first, 2. c4 (69 %) is called the Queen's Gambit (D06). The second, 2. Nf3 (27%) leads to the Queen Pawn Game: Zukertort Variation (D02). Together they account for 96 % of all replies to 1. d4 d5

The 2-5-7-rule

The first three half moves can easily be remembered with a little help from the 2-5-7-rule, saying: there are 2 first moves for White, 5 replies to these 2 first moves (3 for 1. e4 and 2 for 1. d4), and 7 various combinations three half moves down the road. Let's list them.

The 2 first half moves:

• 1. e4 (King's Pawn)
• 1. d4 (Queen Pawn Opening)

The 5 second half move combinations:

• 1. e4 c5 (Sicilian Defense)
• 1. e4 e5 (King Pawn Game)
• 1. e4 e6 (French Defense)
• 1. d4 Nf6 (Indian Game)
• 1. d4 d5 (Queen Pawn Game)

The 7 third half move combinations:

• 1. e4 c5, 2. Nf3 (Sicilian Defense: Misc, Defenses)
• 1. e4 e5, 2. Nf3 (King's Knight Opening)
• 1. e4 e6, 2. d4 (French Defense: Normal Variation)
• 1. d4 Nf6, 2. c4 (Indian Game: Normal Variation)
• 1. d4 Nf6, 2. Nf3 (Indian Game: Knights Variation)
• 1. d4 d5, 2. c4 (Queen's Gambit)
• 1. d4 d5, 2. Nf3 (Queen Pawn Game: Zukertort Variation)

Now let's look at Black's possible replies to these 7 combinations.

Replies to 1. e4 c5, 2. Nf3 (Sicilian Defense: Misc, Defenses)

Here we have three replies: 2...d6, 2...Nc6 and 2...e6. First, 2...d6 (40 %), belonging to the Sicilian Defense: Modern Variations (B50). Secondly, 2...Nc6 (30 %), the Sicilian Defense: Old Sicilian (B30). And thirdly, 2...e6 (26 %), the Sicilian Defense: French Variation (B40). Adding up to 96 % of all Black replies to 1. e4 c5, 2. Nf3

Reply to 1. e4 e5, 2. Nf3 (King's Knight Opening)

This one is easy, with one move, 2...Nc6, making up 85 % of all replies to this line. It's called King's Knight Opening: Normal Variation (C44)

Reply to 1. e4 e6, 2. d4 (French Defense: Normal Variation)

After these first three half moves it's as good as certain that we'll see 2...d5. No less than 98 % of all replies to this line is followed be 2...d5. It's called French Defense: Advance Variation, Steinitz Variation

Replies to 1. d4 Nf6, 2. c4 (Indian Game: Normal Variation)

Here we have two replies: 2...e6 and 2...g6. The first, 2...e6 (46 %) is called the Indian Game: East Indian Defense (E00). The second, 2...g6 (36 %) is the Indian Game: West Indian Defense (E61)

Replies to 1. d4 Nf6, 2. Nf3 (Indian Game: Knights Variation)

Here we have three replies: 2...g6, 2...d5 and 2...e6. The most common is 2...g6 (31 %), called the Indian Game: Pseudo-King's Indian Variation (A49). Second up is 2...d5 (28 %), and according to Chess.com's Master Games Database it has no name. The third one, 2...e6 (26 %) doesn't have a name either. Together these three lines are seen in 86 % of all cases.

Replies to 1. d4 d5, 2. c4 (Queen's Gambit)

For the Queen's Gambit we have two 80 percentile replies: 2...c6 and 2...e6. These two replies occur almost as often. The most common however is 2...c6 (43 %), and it's called the Slav Defense (D10). The second, 2...e6 (38 %) is called the Queen's Gambit Declined (D30). Together these two replies are seen in 81 % of all cases.

Replies to 1. d4 d5, 2. Nf3 (Queen Pawn Game: Zukertort Variation)

Here we have three different replies: 2...Nf6, 2...c6 and 2...e6. The first one, 2...Nf6 is by far the most common, being the reply in 67 % of all cases. It's called the Queen Pawn Game: Symmetrical Variation (D02). The last two replies occur in approximately the same number of cases, 11 % and 10 % respectively. According to the Master Games Database these two replies doesn't have a specific name.

The 2-5-7-15-rule

We can now expand our 2-5-7-rule to the 2-5-7-15-rule, as we two moves (four half moves) down the line have 15 lines in the 80 percentile group. This is actually not so much to remember, especially when you go at it systematically like this. When the game begins White has 20 possible moves to choose between. Luckily, as the 2-5-7-15-rule tells us, we only have to consider 2 of these. Assuming we have 20 possible moves to choose between every move, there would be 400 moves at the second half move, 8,000 at the third half move, and 160,000(!) at the forth half move. That would be impossible to remember. Knowing that we only have to remember a tiny fraction of these, namely 15, is rather fortunate.

The 15 four half move combinations:

• 1. e4 c5, 2. Nf3 d6 (Sicilian Defense: Modern Variation)
• 1. e4 c5, 2. Nf3 Nc6 (Sicilian Defense: Old Sicilian)
• 1. e4 c5, 2. Nf3 e6 (Sicilian Defense: French Variation)
• 1. e4 e5, 2. Nf3 Nc6 (King's Knight Opening: Normal Variation)
• 1. e4 e6, 2. d4 d5 (French Defense: Advance Variation, Steinitz Variation)
• 1. d4 Nf6, 2. c4 e6 (Indian Game: East Indian Defense)
• 1. d4 Nf6, 2. c4 g6 (Indian Game: West Indian Defense)
• 1. d4 Nf6, 2. Nf3 g6 (Indian Game: Pseudo-King's Indian Variation)
• 1. d4 Nf6, 2. Nf3 d5 (Indian Game: Knight Variation???)
• 1. d4 Nf6, 2. Nf3 e6 (Indian Game: Knight Variation???)
• 1. d4 d5, 2. c4 c6 (Slav Defense)
• 1. d4 d5, 2 c4 e6 (Queen's Gambit Declined)
• 1. d4 d5, 2. Nf3 Nf6 (Queen Pawn Game: Symmetrical Variation)
• 1. d4 d5, 2. Nf3 c6 (Queen Pawn Game: Zukertoft Variation???)
• 1. d4 d5, 2. Nf3 e6 (Queen Pawn Game: Zukertoft Variation???)

That's it for now.

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