[fromageGB]

2/1 GF (by agreement) does not have to be absolutely GF. I and probably many others play that 2♣ may not be, with multiple meanings. My 2♣ followed by 2M shows 11/12 and 3 card support, 2♣ followed by 3M shows 13+ and 3 card support. The Bergen type 3-level support responses are therefore 4 cards or more, and I am convinced this is the better approach than having 3-card support in there.

[pescetom]

arepo24, on 2020-May-03, 09:11, said:

Agree. One doesn't necessarily have anything to do with the other.

The majority of bridge players in the world play some form of 2/1.
A search for "Bergen" in Bridge World Standard 2017 produces no results.

[blackshoe]

AL78, on 2020-May-01, 17:53, said:

Having had a quick look on line as to the definition of Bergen raises, I see what you mean. I don't know where she got her current structure from. It appears Bergen was designed with a forcing NT in mind. I don't play forcing NT, so the way to show an invitational raise is to change suit then support partner at the three level. This does seem to negate one of the advantages of the five card major system when holding an invitational hand, the ability to immediately show support with three cards, we end up with the same auction as the four card major Acol players (1M - 2X - 2Y - 3M).

Alan DeSerpa suggested (The Two Club Marionette) playing 2♣ as an artificial bid, a marionette to 2♦, after which responder can show various raises. This replaces 1NT Forcing, and the 1NT response reverts to natural, about 6 to 10 points. Looks interesting, though I haven't had a chance to try it out yet.