Why do earning rates differ for the same booking classes on different partners ?
 

Realize title is a bit unclear... but basic question is why only 2X miles for some airlines in F and 3X for others? I flew SQ in F last week and had expected 3X but only 2X. Other full *A members like NH, LH, OZ, TG, LX etc do give 3X miles. SAA only gives 1.5X for F!

Why??

miles earned on partner airlines for each ticket type
Star Alliance airlines x 3.0 miles x 2.0 miles x 1.5 miles x 1.0 miles x 0.5 miles x 0.25 miles
Adria Airways - C, D, Z - Y, B M, H, Q, V, W, S, E -
Air Canada - J - C,Y,B,H,I,L,M,Q,U,V,O,S,A - -
Air China - F,A,P C,D,Z,J Y,B,M,H,K L,Q,G,S,V,U,W -
Air New Zealand - C, D, J, Z - U,E,O,Y,B,M,H,Q,V,W,T - -
All Nippon Airways F,A C,Z,J,D - Y,B,S,M,K,L,W,G,H - -
Asiana Airlines F, A, P C, D, J, Z - U, Y, E, B, M, H, Q, S, K V, W -
Austrian group - C, D, J - Y, B M, H, Q, V, W, S, G -
Blue 1 - C, A, D, J, Z - Y, S, B, M, H, Q, V, E - W, U, K, L, T, G
Croatia Airlines - C, D, Z - Y, B M, H, Q, V, W, S, G -
LOT Polish Airlines - C,D,Z - Y, B M,H,Q,V,G,W,S E,K,T,L
Lufthansa F,A C,D,Z - Y, B M, H, Q, V, W, S, G, K -
SAS * - C,A,D,J,Z - Y,S,B,M,H,Q,V,E - W,U,K,L,T,G
Shanghai Airlines - F,A C,D,J Y,B,U L,M,T,E,H Q
Singapore - F,P,A,R Z, C, J, D S,Y,B,E,M,H,W,L,K,U - -
South African Airways - - F,P,A,C,D,J,Z Y,S,B,M,K,H,Q T,V,L,W,G -
Spanair - C,D,J,Z Y U, B - M,H,Q,V,L,T,W,K,G
SWISS F,A C,D,J,Z Y,B M,H,U V,G,K,S,Q,L,T,W -
TAP Portugal - - C,D,Z,J Y,B,M,H,Q,V O, U, W, S, K, L -
Thai F,A,P C,D,Z,J - U,Y,Q,M,B,S, H,T,K,G V, W -
United F,A,P C,D - Y,B,H,K,L,M,Q,S,T,V,W,Z,U - -
US Airways F, A C,D,Z - Y,B,U,N,M,H,Q,V,L,W,S,T,P,O,G,E,R - -

* Some routes within Scandinavia are exempt from mileage accrual.


other airline partners x 3.0 miles x 2.0 miles x 1.5 miles x 1.0 miles x 0.5 miles x 0.25 miles
Qatar Airways F,P,A C,J,D Y B L,M,Q,K -
Virgin Atlantic - J,D,Z W,K,S,H B,L,M,Q,V,X,Y N -
Transaero Airlines (LHR-DME only) - C,D,Y,J H M B,Q,I,K,T,X,N,G -
Transaero Airlines (all other routes) - P,J,C,D Y,H M,Q,B,I,K,T,X,N,V,A,L G,R,U -

I've taken the liberty of tweaking your title to make it clearer.

The answer is that different airlines are prepared to "pay" different amounts to frequent flyer programmes for the flights. SQ is quite mean, as is SA.

Also, you might notice that the same flight can earn at different rates depending on which programme you choose to place your miles in. Some of those flights do earn x3 in M&M, for example.