[aopirose]

Out of curiousity, how many of the NPC sororities today were once AES?

Three - ASA, AST and Tri Sigma.

All AES members: ASA, AST, Tri Sigma, Pi Kappa Sigma, Delta Sigma Epsilon, Theta Sigma Upsilon, and Pi Delta Theta.

I know that Sigma Kappa merged with one of the AES sororities (Pi Kappa Sigma). Which was more common, merging or developing into an NPC group?

It was pretty much an even split.

Delta Sigma Epsilon absorbed Pi Delta Theta in 1940 and then DSE was absorbed by Delta Zeta in 1956.

Theta Sigma Upsilon was absorbed by Alpha Gamma Delta in 1959

Pi Kappa Sigma was absorbed by Sigma Kappa in 1959

Also, is there any place I can find more information on Pi Kappa Sigma?

Ask your national historian or HQ archivist. One of them should have access to those records. Good luck.