I have once though that the depreciation of ETH has been caused by the entire crypto market situation. But, as I suspected the faster depreciation rate of ETH, I had a quick research on the endogenous cause of ETH depreciation.
I found out that the ICO (Initial Coin Offering) demand has substantially dropped this year so that Ethereum's demand itself is now experiencing a massive fall out.
By referring to a certain YouTuber's advice in his channel, I switched the majority of my ETHs to BTCs as there is still a growth expectation of the blockchain business and the crypto currency technology.
I left only a few ETHs in case Ethereum may recover to the certain
extend. However, I suspect the entire alternative (crypto) coins including ETH and the other emerging crypto currencies will keep facing a plunge at least for a few days.