Stated another way, SY solves RAE for certain players and creates negative RAE for certain players compared to BY.  | 
							
						
 There is potential for a change beyond just sliding the window. If Sep-Dec are currently quitting, not entering, or otherwise disadvantaged in selection in the sport at a higher rate under BY than May-Aug would under SY, the birthdate distribution will be more imbalanced under BY than it would be under SY. The theory is that this is currently happening because of trapped player issues and the social mismatch across grade levels. As pointed out many, many times in this thread, playing with friends from school is likely to be a bigger motivation to play for players identified as worse (who are more likely to be Q4) than for players identified as better (who are more likely to be Q1). RAE would continue to exist to the extent it depends on the physical/emotional development advantages, which are of course heavily correlated with true age, because it's still just a 12-month window. But there is likely a component causing RAE in the current system that is *not* strictly physical development. It may be hard to pin down an exact definition of "relative age effect," but it's most commonly used as a label for the statistical bias in the group toward the birthdays sooner after the cutoff, i.e., an outcome distribution. Physical development is just one component to explain that bias, albeit the most common one, but there could very well be social or structural explanations as well. This doesn't mean RAE is the reason for the change, and the change doesn't wholly "solve" it, but it may cause a change in RAE which many would consider "lessening" RAE.  | 
							
						
 You don’t solve RAE…  | 
							
						Again, moving from BY to SY solves RAE for some and creates it for others. Merely focusing on the aggregate ignores the dynamics of maximizing of utility for cohorts of individual players. The age cutoff is not and has not been changed to solve RAE. Hopefully SY and BY will exist in such a steady state that RAE is reduced in the future. Like a world with no war, only peace. It would be nice if US Soccer attempted to address RAE. And they have been pretty negligent by doing nothing.  | 
							
						
 You’re overthinking things. Participation and RAE are not connected. This is evidenced by participation drops in all sports regardless of age cutoff. Some sports like tennis, which have rolling age cutoffs with two year age bands mirror the same participation drop offs as all other sports, at the same ages. Nice thought experiment, but the data all says otherwise. Not sure why people have such a hard time grasping what RAE is and instead think of it as some sort of negative pressure or externality, which it isn’t, instead of an observed phenomenon.  | 
							
						
 Again…you don’t “solve” RAE. Just stop. I get what you mean, but you’re saying something different than what you mean. You don’t “solve” RAE.  | 
							
						
 Confidently incorrect.  | 
							
						Confidently incorrect.  | 
							
						From wiki, "The term relative age effect (RAE), also known as birthdate effect or birth date effect, is used to describe a bias, evident in the upper echelons of youth sport and academia, where participation is higher amongst those born earlier in the relevant selection period (and lower for those born later in the selection period) than would be expected from the distribution of births."  | 
							
						
 The bias for those born earlier will still happen. It’ll just happen for the Sep-Dec kids instead of Jan-Mar. It’s not hard to understand.  | 
							
						And the bias affects the probability of participation based on a kid's birthdate which will change with the age cutoff change.  | 
							
						
 Amazing how few understand this simple reality  | 
							
						
 Yes, fewer kids with Jun-Aug birthdays will participate. But more kids with Sep-Dec will participate. In the end it's a wash and RAE effect still there. There is no participation window that solves the problem. It just shift it to a different set of kids. That is life.  | 
| The RAE shifts but participation may not dip because fie the most part, those June - Aug birthdays will be playing with kids in the same grade. Not classmates specifically, which is where most people go off the rails when discussing the age change. Same class as in they get phones around the same time, they they start liking the opposite sex around the same time, etc… insert whatever social activity kids share with kids in their class range at school. That affects the participation early on. | 
							
						
 Dumb dumb posts a wiki and thinks he is the at least now an expert enough to justify being second author on future RAE studies. You don’t “solve” RAE. And participation and RAE are not casually related. There are studies on this you can spend your free time perusing opposed to assuming Wikipedia makes you an expert.  |