上周四比特幣崩盤。截至正午（美國東部時間），比特幣兌美元匯率在短短兩個小時的瘋狂交易中共下跌20%。

近些天的火熱行情給比特幣帶來的漲幅幾乎損失殆盡，原因看來是人們擔心中國將采取新的措施來抑制資金外流。中國占比特幣公開交易的90%以上，約70%的比特幣“挖礦”活動（通過創建區塊鏈來生產比特幣，區塊鏈是比特幣的底層技術基礎）都集中在中國。因此，最近比特幣劇烈波動的源頭不太可能在其他地方。

雖然不可能鎖定比特幣飆升的確切源頭和動力，但有足夠跡象說明影響比特幣走勢的終極因素就是人民幣。2016年11月以來人民幣匯率急劇下滑，但最近兩天出現反彈，原因是中國央行大力軋空讓投機者產生了些許恐懼。

上周一美元匯率逼近7元人民幣。周四，人民幣反彈逾2.5%，香港離岸市場美元/人民幣報6.81。比特幣市場的流動性和透明度遠不如匯市，它將人民幣匯率的猛然反轉放大了許多倍。

正如分析師們所說，大家都意識到比特幣“將要回落”。2016年12月21日以來，比特幣兌美元上升了45%；2015年9月至今的增幅更是達到了令人側目的521%。在此期間，美元兌其他貨幣幾乎全線走強，這讓比特幣的走勢顯得更加震撼。

問題在于，這樣的行情會引發回調嗎？為了讓人民幣放緩下行腳步，政府部門就新資本管制措施發出的提醒和暗示看來就是答案。

新年到來之際，中國人民銀行宣布，將金融機構大額現金交易報備門檻從20萬元人民幣下調至5萬元人民幣（7100美元）。央行表示，此舉只是為了加大對洗錢、偷逃稅等犯罪活動的監測和打擊力度。同時，外管局細化了個人外匯信息申報內容，個人購匯（每年每人額度為5萬美元）時需說明購匯理由以及所購外匯的使用地點與使用方式。

雖然一年半以來一直允許人民幣貶值，但中國政府不愿意看到局勢陷入混亂，因為這既有可能在國內引發恐慌，也有可能造成美國新任總統再次指責中國操縱貨幣。

實際上，在這一年半時間里中國一直在推動人民幣升值，而非壓低其匯率。2016年1-10月中國資本外流規模猛增至5300億美元，中國外匯儲備則從2014年初略低于4萬億美元的高點下降近25%。分析師估算，僅11月份，中國央行就動用了超過340億美元外匯儲備來支撐人民幣匯率。同時，預計外管局本周公布的數據將表明，中國外儲自2011年以來首次跌至3萬億美元以下。

2015年8月人民幣兌美元貶值2%，這是中國幾年來首次調整匯率，隨后中國政府下在人民幣上的賭注就像雪球一樣越滾越大。同時，如下圖所示，人民幣和比特幣兌美元的匯率也越發緊密地聯系在了一起（只是按百分比計算，比特幣的增幅當然要大得多）。

The value of the cryptocurrency bitcoin is melting down Thursday, having dropped 20% against the dollar by midday Eastern Time in only two hours of frantic trading.

The move reversed an almost equally feverish rise in recent days that had appeared to be driven by concerns that China will introduce new measures to stop its citizens moving money out of the country. China accounts for over 90% of reported bitcoin trades and around 70% of bitcoin "mining" (the production of new bitcoins through the building of blockchain that makes up the currency's infrastructure). So it's unlikely that the source of recent volatility lies anywhere else.

While it's impossible to pin down the exact source and motive for the bitcoin rally, there are plenty of signs that what's going on with bitcoin is, ultimately, driven by what's going on with China's official currency, the renminbi (also known as the yuan). The renminbi has fallen sharply since November but rallied over the last two days thanks to a brutal short squeeze engineered by China's central bank to put a bit of fear into speculators.

After nearly touching 7 to the dollar on Monday, the renminbi rallied over 2.5% Thursday to reach 6.81 in the offshore Hong Kong market. That abrupt reversal was magnified many times over in a bitcoin market that doesn't have anything like the same liquidity or transparency as the market for official currencies.

By anyone's reckoning, bitcoin was, as the analysts say, "due a correction." It had risen by 45% against the dollar since Dec. 21, and by an eye-watering 521% since September 2015. Those moves are all the more striking because the dollar has strengthened against virtually every other national currency in the world in that time.

The question was, what would trigger the correction? The answer appears to have been a series of nudges and winks from the authorities about the introduction of new capital controls to slow the renminbi's decline.

Over the new year, the People's Bank of China, China's central bank, said that banks will be required to notify it of all cash transactions over 50,000 yuan ($7,100), down from a current ceiling of 200,000 yuan. It said the move was merely aimed at improving the monitoring of money-laundering and tax fraud. Meanwhile, the State Administration for Foreign Exchange (SAFE) imposed onerous new reporting requirements requiring people to explain why, where and how they intend to use their annual quota of foreign currency (which is capped at $50,000 per person).

While Beijing has allowed the renminbi to weaken over the last 18 months, it doesn't want a disorderly rout that would both trigger panic at home and invite fresh accusations of currency manipulation from the new U.S. President.

The fact is, such manipulating as Beijing has done over the last 18 months has been to support the renminbi rather than weaken it. Capital outflows from China in the first 10 months of 2016 rocketed to an estimated $530 billion, while the country's stash of foreign reserves has fallen nearly 25% from a peak of just under $4 trillion in early 2014. Analysts estimate that the PBOC spent over $34 billion in November alone to prop up the currency, and figures expected next week from SAFE are expected to show reserves dropping below $3 trillion for the first time since 2011.

Chinese bets against the renminbi have snowballed since Beijing let it fall by 2% against the dollar in August 2015, the first revaluation in years. And, as this chart shows, the renminbi and the bitcoin rate to the dollar have become increasingly closely correlated (though bitcoin's rise, in percentage terms, has of course been far more dramatic).

現在，這種關聯性再一次戲劇性地得到了證實。如果中國真的打算為了資本管制而切斷比特幣交易，由此產生的結果就確實非常令人期待。（財富中文網）

作者：Geoffrey Smith

譯者：Charlie

審校：詹妮

Today, once again, that correlation was affirmed, dramatically. If ever China actually tries to close down bitcoin exchanges as a form of capital control, the fallout will be truly exciting to watch.