> As more of the tokens are mined, the puzzles get harder Difficulty doesn't automatically increase over time. Rather, it has tended to increase for two major

> As more of the tokens are mined, the puzzles get harder Difficulty doesn't automatically increase over time. Rather, it has tended to increase for two major reasons: 1) bitcoin price going up, increasing miner competition chasing the higher reward. The reward halvings every 4 years have done little to counter this uptrend. 2) mining efficiency going up. after transitioning from CPUs through GPUs and FPGAs to ASICs, efficiencies have started to level off now.