Learners are often more accurate in using plural -s than in using possessive -s’.
Learners are often more accurate in using -ing than in using -ed past.
The learner’s L1 has some effect on the accuracy order of grammatical morphemes; however, it is not entirely determined by the learner’s L1. There are some strong patterns of similarity among learners of different L1 backgrounds.
(* Please see p. 5 for the L1 development of grammatical morphemes)