Lets prove it by an example.
Take a coin and toss it 10 times. Note down the number of head and tails it has shown in ten tosses. It can be like 3 head +7 tails , or, 4 tails + 6 heads..it can be any number.
Now flip the coin for at least 1000 times and note all the outcomes..the difference between head and tails will decrease. AND ..After sufficient number of tosses of the coin the count of head and tail will be almost equal.
Here the number of tosses represent the number of traders..higher the number of trader , natural will be the outcome i.e equal number of head and tail.
This is called Law of Nature..Law of Equilibrium ..Law of everything.