How to read it

The top panel puts BTC and the indices on separate axes. They have to be separate: the Dow is a five-figure number, the S&P is four, and Bitcoin has spent this history crossing several orders of magnitude. Sharing one axis would flatten whichever series is smaller into a straight line. Use the axis selector to choose which side a drag-zoom applies to.

The middle panel is the honest comparison: BTC priced in units of an index. It takes the dollar out of both sides, so a rising line means Bitcoin is genuinely outperforming that market rather than both simply being repriced by the same currency.

The bottom panel is a 252-market-day rolling z-score of that ratio - how stretched the relationship is against its own last twelve months. The ratio is logged before scoring, which matters: a ratio is floored at zero and unbounded above, so scoring it raw would read as permanently positive through any uptrend. In logs a halving and a doubling are symmetric, which is what an oscillator needs.

The window is deliberately a year rather than all history. Over the full sample Bitcoin's early orders of magnitude dominate, and the score would sit pinned near the top of its range for a decade without telling you anything.

The fourth panel is a 90-day rolling correlation of daily returns - not of price levels. That distinction is the whole point: two things that both went up over a decade have level-correlation near 1 whatever they did day to day, so measuring levels would tell you about shared trend rather than shared behaviour. On returns, 0 means they move independently and 1 means in lockstep, which is the question people actually mean by “is Bitcoin trading like a tech stock?”

The power law fit button on the ratio panel overlays an OLS regression of log(ratio) against log(days since genesis) - the same shape as the price power law, applied to a unitless quantity. Treat the R² on it with suspicion: a trend fitted to a ratio of two trending series will almost always look tidy, and it carries no claim that the relationship continues.

BTC daily closes from Coin Metrics; index closes from Yahoo Finance. Aligned to market days, since the indices don't trade weekends - a weekend Bitcoin move lands on the next open. Index levels are price returns only and exclude dividends, so the ratio modestly flatters Bitcoin over long spans. Not financial advice.