BTC ROI Since Peak: 0.651
How far the price has fallen from each cycle's record high, with every downturn lined up at its peak. 1.0 means back at the record; 0.25 means down 75%.
Each line takes one cycle's highest price as 1.0 and shows the price as a fraction of it from that day onward. All the lines start at their own peak, so you can compare how deep and how long each downturn ran.
For example, if the current line reads 0.65 nine months after the peak, the price is 35% **below** its record — and reading straight across shows the 2017 line was at 0.30 at the same point, so that downturn had already been far worse. Past downturns bottomed around 0.15 to 0.25, a fall of 75% to 85%, and took roughly 12 to 18 months from peak to trough.
Four downturns **is not** enough to make that a rule.
In words: inside each halving period find the highest price, then draw the price as a fraction of that high from the peak day onward, with every cycle's peak aligned at the same starting point.
The current cycle's peak is simply the highest price so far, so the whole current line is rebased if a new record is set. Finished older cycles are unaffected.
Our own full BTC price history (btc_price_daily: blockchain.info daily closes, 2010-08 to today, 5800+ points). No external API at request time.
Own compute · full BTC price history 2010+ (no external API)