← Back to Blog · 2026-10-08 · 8 min read · Strategy Case Study

Picture this: you're long thermal coal futures in October 2021. The trend has been your friend for months. Your breakout system is printing entries, your equity curve is pointing up and to the right, and then — almost overnight — the government announces price intervention, the exchange hikes margins, and your position gaps limit-down. Three days in a row. No stop-loss gets filled. No graceful exit. Just a locked door between you and the exit.

This isn't a hypothetical nightmare. It's roughly what happened to traders on both sides of the 2021 thermal coal trade in Chinese commodity futures. And it's one of the best stress tests a momentum trader can study, because it broke the strategy in two completely different ways: first on the way up (the short squeeze), then on the way down (the policy reversal).

Let's walk through it like we'd dissect any trade review — with real contract mechanics, concrete rules, and the uncomfortable lessons most backtests never show you.

What Actually Happened in 2021

The setup was macro, not technical. China's post-pandemic industrial recovery collided with an energy supply crunch: coal production was constrained, imports were tight, and electricity demand surged. Thermal coal futures on the Zhengzhou Stock Exchange (ZCE) — the ZC contract, 100 tons per lot, quoted in yuan per ton — became the epicenter of one of the most violent rallies in Chinese commodity futures history.

Through the second half of 2021, the contract roughly multiplied in value from where it had traded earlier in the year. The move wasn't a smooth trend — it was a staircase of limit-up days, gaps, and violent pullbacks that shook out anyone trading with tight stops. Shorts who faded the rally kept getting squeezed: every time price looked exhausted, another limit-up day trapped them again.

Then came the reversal. Around mid-to-late October 2021, China's National Development and Reform Commission (NDRC) signaled aggressive intervention in coal pricing — studying ways to cap prices and, effectively, telling the market the party was over. The exchange raised margin requirements and narrowed price limits in response to the volatility. The result: thermal coal futures collapsed in a cascade of limit-down days. Longs who had ridden the trend up couldn't get out at any reasonable price. The correction was severe and fast — the kind of move that erases months of trend-following profits in a week.

Two phases, one contract. Let's run a momentum strategy through both.

The Strategy: A Simple, Honest Momentum System

To make this a fair test, we'll use a deliberately vanilla momentum system — the kind you could code in an afternoon. No machine learning, no curve-fitted magic:

• Entry: Go long when price closes above the highest high of the previous 20 sessions. Go short on the mirror image (close below the 20-day low).
• Exit: A close below the 10-day low exits longs (and vice versa for shorts). No profit targets — we're letting the trend run.
• Risk per trade: Risk roughly 1% of account equity per position, sizing off the distance to the exit level.
• Instrument: One position at a time in ZC thermal coal, no pyramiding, no averaging down.

This is close to a classic Donchian/turtle-style approach. It's robust, it's been tested across decades and markets, and — crucially for this case study — it has no opinion about governments, coal supply, or NDRC press conferences. It just follows price.

Phase One: The Rally and the Short Squeeze

On the way up, the momentum system did exactly what it's designed to do. Each 20-day breakout triggered a long entry. Each subsequent limit-up day added to the paper profit. The 10-day-low trailing exit was wide enough to survive the violent pullbacks that stopped out every counter-trend short trying to pick the top.

And that's the first half of the lesson: the short squeeze punished exactly the traders momentum traders love to see punished. Fading a parabolic move in Chinese commodity futures is a coin flip at best, because limit-up days mean shorts can't cover even if they want to. The mechanics of the ZCE price limit system — daily limits on how far price can move, which were tightened during the 2021 volatility — mean that a squeezed short doesn't just lose money, they lose control. They can't exit. Their loss compounds at the limit price while they watch.

A momentum long, meanwhile, had the opposite experience: the limit moves were working for them. The system's trailing exit kept it long through the entire staircase. By the time the NDRC headlines hit, the position had accumulated a substantial open profit.

So far, so good. Momentum looks brilliant. Now comes the part that matters.

Phase Two: The Policy Reversal — Where the Strategy Breaks

Here's the honest accounting. When the policy reversal hit, the momentum system's exit rule — a close below the 10-day low — could not execute at anything close to the price on the chart. The contract went limit-down. Then again. Then again. On the ZCE, when a contract closes at its limit with the order book still stacked against you, your exit order sits in a queue behind everyone else trying to do the same thing.

Three things happened simultaneously:

• Slippage became structural, not incidental. The backtest says "exit at the 10-day low." Reality said "exit several limit-down days later, at a price far below your last marked-to-market equity."
• Margin requirements jumped. The exchange raised margins precisely when positions were underwater, forcing some traders to reduce or liquidate at the worst possible moment. Higher margin on a losing position is a margin call with extra steps.
• Liquidity evaporated. In a limit-down environment, buyers disappear. Volume dries up at the limit price. Your 100-ton lots, trivially liquid during the rally, became nearly unsellable.

Would the system have survived? Probably — if position sizing was genuinely conservative. A 1%-risk-per-trade framework means even a catastrophic gap of several limit moves shouldn't blow up the account. But the profit give-back would have been brutal: a large chunk of the trend's gains, gone in days. The equity curve would show a smooth climb followed by a cliff — not because the entry logic failed, but because exits in Chinese commodity futures are not always executable.

The Lessons That Actually Transfer

This case study isn't an argument against momentum. It's an argument for building momentum systems that respect the specific plumbing of China futures. Here's what I'd take from 2021 thermal coal:

1. Policy risk is a position-sizing input, not a footnote

In Western markets, we treat regulation as background noise. In Chinese commodity futures, policy is a first-order price driver. The NDRC has repeatedly demonstrated willingness to intervene directly in commodity prices — coal in 2021, iron ore during earlier price surges, and other staples at various points. If you trade rebar, iron ore, or thermal coal, you should size positions as if a policy headline can invalidate your thesis overnight, because it can and periodically does.

2. Limit days change your true risk number

Your stop-loss is not your risk. Your risk is the distance between your entry and the price you can actually exit at, which during limit sequences can be multiples of your intended stop. A practical adjustment: when a contract has recently traded at its limit — up or down — cut position size. The 2021 thermal coal contract was flashing this warning for weeks before the reversal, with repeated limit-up days signaling a market where normal two-way price discovery had broken down.

3. Exchange margin hikes are a signal, not just a cost

Chinese exchanges raise margin requirements and adjust price limits as volatility-management tools, often before the biggest moves. When the ZCE hiked thermal coal margins in late 2021, it was the market infrastructure itself telling you that conditions had become abnormal. A disciplined trader can treat margin changes as a regime flag: reduce size or tighten exposure when the exchange starts firefighting.

4. Trailing exits need an "unfillable" contingency

Consider adding a rule most retail systems lack: if your exit triggers on a limit-down day and you can't get filled, your next-session behavior should be pre-programmed — exit at the open regardless, or exit on the first session where the contract doesn't close at its limit. Decide in advance. The worst outcome in a policy reversal is improvising while your equity is being repriced downward every session.

5. The trend side still paid

Worth saying clearly: even after the give-back, a momentum trader who entered early and sized conservatively likely kept a meaningful share of the rally's gains. The strategy didn't fail — it just delivered its returns in a lumpier, uglier package than a backtest would suggest. That's the realistic expectation for trend-following in Chinese commodity futures: big dispersion between paper results and lived results, driven almost entirely by exit mechanics.

How You'd Apply This to Rebar, Iron Ore, and Beyond

The 2021 thermal coal episode is extreme, but the mechanics generalize across Chinese commodity futures:

• Rebar and iron ore on the Shanghai and Dalian exchanges respond to the same policy dynamics — infrastructure stimulus, production restrictions, environmental mandates. Momentum works, but policy headlines can create the same gap-and-limit sequences.
• Check the contract specs before sizing. Thermal coal was 100 tons per lot with a 0.2 yuan/ton tick on ZCE; rebar is 10 tons per lot with a 1 yuan/ton tick on SHFE; iron ore is 100 tons per lot on DCE. The tick value and multiplier determine how precisely you can size a 1%-risk position — and whether small accounts can trade the contract at all without over-sizing.
• Respect the price limit regime. Chinese exchanges use daily price limits and dynamic margin adjustments as standing tools. Build your risk model around the limit, not around the assumption of continuous liquidity.
• Backtest with limit-day awareness. If your backtest fills your exit at the limit price on a locked-limit day, it's lying to you. Model those fills at the next tradable price, at minimum.

Momentum remains one of the few approaches with credible long-run evidence across markets, and Chinese commodity futures — with their strong, persistent trends driven by real industrial demand and policy cycles — are fertile ground for it. But 2021 thermal coal is the reminder that the ground shifts.

The Takeaway

A momentum strategy would have made real money on the 2021 thermal coal rally, survived the policy reversal if — and only if — position sizing was genuinely conservative, and given back a painful chunk of profits to limit-down mechanics that no stop-loss could fix. That's not a failure; that's the honest cost of trading a market where the government is a participant and the exchange actively manages volatility.

The traders who come out ahead aren't the ones with the cleverest entry signal. They're the ones who sized for the gap, read margin hikes as signals, and had an exit contingency written down before the first limit-down day.

If you're running a system like this and want to see how it holds up against real Chinese market data — the limit days, the margin changes, the policy shocks — that's exactly what we built XS Select for. It's a China futures evaluation platform where you can test your rules on real historical data, with evaluations starting from $29. No pressure either way — but if 2021 thermal coal taught us anything, it's that you want to find the holes in your system before the market does.