It always strikes me as a bit strange that the annuals didn't start until after the show had finished. It was so popular during its run you'd have thought they might have at least put one out in 1972.
That's because annuals are cover dated a year ahead. The 1973 annual came out in late 1972. Annuals had to have all their copy checked off by February, with illustration work (at this point done in-house at World's headquarters in Manchester) taking a few more months, then printing and distribution ready to go on sale in September.
Being shown in the summer months, it would not have been possible to get a Follyfoot annual out for late 1971 so the earliest would have been in the shops in late 1972, cover dated 1973.