[Knurdler]

Larry Cohen tells me that opening a minor playing Standard American: 1 diamond will be 4 or more cards 97% of the time and 1 club will be 4 or more 83% of the time.

My partner is one of those who insist 1 diamond is 4 cards so we sometimes open 1 club with only 2 cards and announce it as could be short.
Clearly our 4+ diamond percentage rises to 100%.
Can anyone tell me what our 4+ club percentage probability falls to?

Very few here play better minor.
Their better minor means they always open the longer minor but if they are equal length, they open the stronger one.
Can anyone tell me the percentages for 4+ diamonds or 4+ clubs playing this type of better minor?

Thanks

[DavidKok]

Assuming a 15-17 NT, and better minor simply means more HCP in the suit, ties going to clubs, your 1♣ opening is:

• 2 cards: 4.1%
  
• 3 cards: 16.2%
  
• 4 cards: 33.7%
  
• 5 cards: 39.5%
  
• 6 cards: 18.1%
  
• 7 cards: 3.8%
  
• 8+ cards: 0.5%

In my experience most people glance at a table like this and then claim that, regardless of what the numbers are, that it is good enough to disregard the '2 cards' component.
Most five card major systems are really 5543 systems - the 1♠ and 1♥ opening promise 5, the 1♦ opening promises 4, and the 1♣ opening promises 3, and with a 4=4=3=2-distribution outside your NT range you need a systemic lie but it is inefficient to cater to it with the rest of your system. Personally I prefer to make 1♦ 5(+) almost always, which increases the frequency with which 1♣ is two. I think previously(?) the ACBL also had different rules for a 'can be 2' 1♣ opening and an 'always 3+' 1♣ opening, and in that case if you are playing a 5543-system anyway you may as well break ties towards diamonds to get some regulatory protection. But maybe they changed this? At any rate it does to me not matter where you put 4=4=3=2, it's almost entirely symbolic.

[awm]

It’s important to remember, though, that these numbers are not independent from the other distributions at the table. For example, if your partner opens 1♣ and you have 5♣ and want to decide how high to raise, it becomes quite a bit more than 4% that partner has only two and 20% that partner has three or fewer.

[DavidKok]

Conditioning on responder having exactly five clubs I get:

• 2 cards: 8.6%
  
• 3 cards: 25.5%
  
• 4 cards: 35.3%
  
• 5 cards: 24.4%
  
• 6 cards: 5.8%
  
• 7 cards: 0.5%
  
• 8+ cards: 0.0% (after rounding)

If you're a glass half full sort of persion this is a 91+% chance of at least an eight card fit. If you're a half glass empty sort of person this is a more than doubling of the doubleton rate, with almost 35% chance of not having a 9-card fit. At any rate, these are the numbers (using my assumptions for the simulation, which are of course a simplification of real opening criteria).
If you condition on an opponent having an overcall or a takeout double of 1♣ the odds shift in favour of the opening showing actual clubs again, which is probably the most important scenario for deciding when and how high to raise. Giving direct seat overcaller a 1M overcall and responder exactly 5 clubs shifts the odds back again:

• 2 cards: 5.1%
  
• 3 cards: 19.4%
  
• 4 cards: 36.3%
  
• 5 cards: 31.1%
  
• 6 cards: 7.5%
  
• 7 cards: 0.6%
  
• 8+ cards: 0.0% (after rounding)

You decide which table is most informative for the scenario you are thinking of.