Bitcoin resumed declines on Jan 13 as the digital coin heads for its worst week since March last year, casting doubt on the outlook for the cryptocurrency boom.

Bitcoin fell as much as 6.8% to about US$32,359 ($42,817) before paring some losses, according to a composite of prices compiled by Bloomberg. The largest cryptocurrency hit a record of almost US$42,000 on Jan 8 before tumbling to a low around US$30,300. The Bloomberg Galaxy Crypto Index fell as much as 7.1%.

The price swings evoke memories of Bitcoin’s December 2017 bubble that was followed by a rapid collapse. They also test recent narratives, such as the argument that Bitcoin is maturing into a hedge against dollar weakness and inflation risk, and attracting longer term investors.

See: Is the bitcoin rally over?

An alternative view is that fast money seeking rapid gains helped to propel the quadrupling in Bitcoin over the past year, leaving the rally exposed to the risk of such investors pulling out as momentum wanes.

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“Taking some profits off the table after an asset — any asset, not only Bitcoin — doubles in value within three weeks is completely understandable,” said Julius de Kempenaer, senior technical analyst at StockCharts.

Bitcoin could reach US$146,000 long term as it competes with gold as an asset class if swings in the digital asset moderate sufficiently to lure more institutional investors, JPMorgan Chase & Co. strategists said this month. They also flagged signs of froth that could lead to a pullback in the shorter term.