As block reward decreases, miners will be dependent on transaction fees to suffice for their electricity costs. By then, if the price of Bitcoin isn't high enough, it will lead to a further reduction as miners abandon their business because of the lack of profit.
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Further reduction?
Further reduction in what? Why would it matter if some miners abandon their business?
If a sufficient amount of miners leave the Bitcoin network, then there would not be enough to confirm pending transactions and mempools would grow massive. This isn't efficient.