Can Circulating supply decrease?
Shouldn't Market Cap increase when price increases?


It depends. MarketCap = circulating supply x unit price

Giving : MC=10, CS=10, UP=1

Example of an increase in MC : MC=20, CS=10, UP=2

Example of steady MC : MC=10, CS=20, UP=0.5

Example of a decrease in MC : MC=5, CS=10, UP=0.5


  Can circulating supply decrease?


Yes circulating supply decrease, especially in centralized coins(controlled by individuals or corporations)

Example : Ripple decided to lock a huge number for XRP in mid 2017 which lead to unit price increase