Why is it...weight differences only matter below 200lb...?

They should bring back the Super Heavyweight division. oh dear god no this again...

AT HW it can matter but in most cases if one is significantly bigger...it's usually because he's out of shape.

The real reason is because there's a certain cut off at which point height/weight becomes inversely proportional to skill. So that the larger you are, the less skilled you are due to the sheer inability of the human body at such weights to be able to be efficient and move with speed. So a 400lbs does not have a "advantage" over someone 200lbs because that 400lbs person will be slow as molasses and easy to KO

if you think a 10 lb advantage in weight at HW is the same as a 10 lb weight advantage at WW you're an idiot. you're not an idiot, are you?

Weight classes are in place to deal with weight advantages and to level the field when it comes to bone/muscle structure, and height. I think due to the origins of the sport's rules (to make fights fair due to the appearance of size) the weight classes and the implications of these classes coincidentally also match up with the science of power and how it affects knockouts. There are always some outliers with super heavy/light bones (which results in more or less muscle mass), super tall/short bones (more or less reach) etc. In general people who are taller and weight more will have more power. This is due to the equation for Power (Power= Mass (overall mass) x Acceleration). The reason why there are no weight classes beyond 200lbs is that few people in the past due to nutritional and chemical factors were not able to compete athletically in boxing. Once certain populations increased their living standards (China is a great example) their populations begin to increase in height. During the times of Napoleon Bonaparte the average European was around 5"4-5"6. At the same time there is a level at which even a minimum amount of mass in the weight class results in knockout power. So in theory a light puncher at lightweight with a low ko percentage, when moved proportionally up to a certain weight (I don't believe it is exactly at 200lbs but I imagine it is close to that weight) should have an increased KO ratio as the skulls of both the lightweight and the heavyweight counterpart are made of similar mineral compositions (bone), have similar integrity (construction) and are put together in similar fashion (in this case since it is the same fighter they are identical so the bones and muscles form the skull in the same way). I don't believe this is the actual reasoning for the weight classes but it is the reason that certain fighters can move up in weight and others can't. It is also the reason why people don't make such a big deal about weight discrepancies at heavyweight and they do at welter for example. A KO is a concussion. A concussion happens when your brain hits your skull. Your brain floats in liquid like a balloon on a string. When your skull hits your brain hard enough you're knock-out. After a certain point it doesn't matter how big you are. Yes, being bigger allows you to absorb more body blows but aside from some people having extra dense skulls, which would slow the acceleration of the skull, being bigger does not help you. The previous statement about denser skull is my speculation. There is no proof that I know of. Yes a longer reach is useful but look at Dempsey v Willard. Dempsey f**ked him up. Say what you will about early fighters but a "small" heavyweight damn near killed a "big" heavyweight.

The weight classes need to be updated, when one pro fighter out weighs another by 20lbs it makes a difference, I don't care what anyone says.

Weight classes are in place to deal with weight advantages and to level the field when it comes to bone/muscle structure, and height. I think due to the origins of the sport's rules (to make fights fair due to the appearance of size) the weight classes and the implications of these classes coincidentally also match up with the science of power and how it affects knockouts. There are always some outliers with super heavy/light bones (which results in more or less muscle mass), super tall/short bones (more or less reach) etc. In general people who are taller and weight more will have more power. This is due to the equation for Power (Power= Mass (overall mass) x Acceleration). The reason why there are no weight classes beyond 200lbs is that few people in the past due to nutritional and chemical factors were not able to compete athletically in boxing. Once certain populations increased their living standards (China is a great example) their populations begin to increase in height. During the times of Napoleon Bonaparte the average European was around 5"4-5"6. At the same time there is a level at which even a minimum amount of mass in the weight class results in knockout power. So in theory a light puncher at lightweight with a low ko percentage, when moved proportionally up to a certain weight (I don't believe it is exactly at 200lbs but I imagine it is close to that weight) should have an increased KO ratio as the skulls of both the lightweight and the heavyweight counterpart are made of similar mineral compositions (bone), have similar integrity (construction) and are put together in similar fashion (in this case since it is the same fighter they are identical so the bones and muscles form the skull in the same way). I don't believe this is the actual reasoning for the weight classes but it is the reason that certain fighters can move up in weight and others can't. It is also the reason why people don't make such a big deal about weight discrepancies at heavyweight and they do at welter for example.