The Simpsons on Channel 4

Does anyone know the exact terms of the contract channel 4 signed to buy the terrestial rights for the simpsons? The pattern has been very similar to BBC 2, with a series of "new" episodes (about four years old) once a year, with repeats the rest of the year. surely they should be allowed to show all episodes up to (but not including) the most recent series on sky. anyone think channel 4 have been sold a pup?

Channel 4 has rights for seasons 1 thru 12. season 16 just ended the states (sky 1 now showing episodes from the start of that season)

Channel 4 showed season 12 from start to end every friday at 9, when it was over they have now jumped back and are showing season 11.
I have them all anyway (including season 16 as of yesterday) so non of it matters to me

It seems very far behind the states. Even if Sky have first rights, on most other shows they are shown just a few months later.

I think I worked out C4 could show about six or seven series back to back on a weekly basis with no danger of catching up Sky.