That would explain why I had some fortresses with a lot of skilled migrants, and some with none. I prefer longer histories but sometimes the world stops much sooner than 1050, and a couple of times I made pocket worlds to see if I could live with those. But even at 1050 not all of my migrants are skilled.
Not counting my original 7, these were the highest skill levels for each Dwarf present in the Spring saves of the fortress I am currently playing, as read by Dwarf Therapist. It is a higher level overall than I remembered, due to the fact that I tend to ignore military skills. By 1053 everyone is building social skills so there are no longer any complete Novices, but that is not useful to the fortress. A lot of the ones who are Competent and below have only social, and sometimes military, skills. Some of the higher ones have industrial skills useless to me, such as the High Master in Pump Operating, who is working for me as a Competent Mechanic. Those still count as far as this discussion goes, however. I have noted some professions because they are heavily used in my fortress and the skill level reflects that. Some of the undescribed higher levels are in social skills, but not all.
1052:1 Master, 2 Great (1 a Planter), 1 Adept, 2 Adequate, 4 Novice
1053:2 Legendary +5 (both Stonecrafters), 1 Legendary +2 (Mason), 1 Legendary +1 (Miner), 1 High Master (Planter), 6 Master, 7 Great, 1 Expert (Planter), 2 Skilled, 14 Competent, 11 Adequate (2 are children), 13 Dabbling (all children)
1054:2 Legendary +5 (both Stonecrafters), 2 Legendary +4 (1 Planter and 1 Stonecrafter), 1 Legendary +2 (Mason), 1 Legendary +1 (Miner), 1 Grand Master (Planter), 3 High Master, 9 Master, 5 Great, 1 Adept, 2 Talented, 2 Proficient, 10 Skilled (2 are children), 19 Competent, 4 Adequate, 4 Novice (3 are children), 29 Dabbling (all children)