Stack Flip: When Price Crosses the 200-Day Moving Average
A <strong>stack flip</strong> happens when an instrument's price crosses one of its major moving averages — most often the 200-day SMA. The flip is a binary state change: a name that was structurally above its 200-day is now below it, or vice versa. It is one of the oldest and most-watched regime markers in technical analysis, and Closelook logs every one as a discrete event.
What the stack represents
Most long-term trend filters use three moving averages together: 20-day, 50-day, and 200-day. Their relative ordering defines the "stack." When price is above all three in ascending order (20 > 50 > 200), the instrument is in a confirmed uptrend. When price is below all three in descending order, a confirmed downtrend. Mixed states — above the 50 but below the 200, or vice versa — are transitions.
What Closelook tracks
The Temperature worker tags each instrument with a categorical stack state on every daily snapshot. The most important transitions are:
- above_50_200 → near_200 or below_200: a structural weakening. Longs lose their long-term trend anchor.
- below_200 → near_200 or above_50_200: a structural recovery. Often the first sign of a regime shift off a bottom.
- above_50_200 → above_200_below_50: a short-term weakness without losing the long-term trend. Many genuine pullbacks sit in this zone.
Every flip is logged as an event in the Lab's event timeline, with the instrument, the before and after states, and the date.
How to read a stack flip
Stack flips are state changes, not price predictions. Price can flip above the 200-day and keep going, or it can flip and immediately revert — the flip itself doesn't tell you which. What it does tell you is that a previously-true structural claim (this instrument is in a downtrend) is no longer true. Portfolios built on that claim need to revisit.
Context matters. A flip that happens on rising volume with confirming momentum is far more reliable than a flip on thin volume with bearish divergence. The Lab's event timeline pairs stack flips with the other signals active at the same moment so you can see the full context.
Why it matters
The 200-day SMA is a schelling point — thousands of traders, algorithms, and mandate-driven institutions watch it. This makes flips across it self-reinforcing: once price crosses, position-driven buying or selling often extends the move in the direction of the flip for several sessions. That doesn't make the signal predictive, but it does make it consequential. Ignoring flips in major macro instruments (SPY, QQQ, TLT, GLD) means missing the moments when regimes visibly change.