I have another theory for the offside calls correlation. More offside calls could correlate to, not only more aggressive offside traps, but also more cherry-picking attackers. (Roy Lassiter and Mamadou Diallo come to mind.) These players are going to try to beat the offside trap every time, and even if they're offside most of the time, they will beat the offside trap sometimes. This leads to more breakaway opportunities. In the current MLS, I see a lot more goals coming from combination plays and less from breakaways. I used to sort MLS goals by MLSnet match report descriptions. The "breakaway" column in recent seasons is a lot shorter than in previous years. I don't know where my old data went - I suspect a lot of it got destroyed by a hard disk glitch a couple years ago. But I know that, in one of the earlier seasons, as many as 8% of all MLS goals were scored on breakaways, and in the current season (with my analysis now aided by video) it's been only 2.8% so far. Incidentally, the percentage of goals scored by headers has gone up dramatically - near 20% this season, compared to 14.8% in 2003 and around 12% in the first few seasons.