Crypto glossary
Logarithmic chart (log scale)
A logarithmic chart spaces prices by percentage change rather than absolute amount, so a doubling looks the same at any price level.
On a linear chart, the distance from 10 to 20 dollars equals the distance from 100 to 110. On a log scale, the move from 10 to 20 dollars takes the same vertical space as the move from 100 to 200, because both are a 100% gain. This makes it possible to compare moves across very different price levels on the same chart.
Log scale is the norm for long-term bitcoin charts, since the price has risen by many orders of magnitude since 2010. On a linear chart, everything before the last cycle looks flat; on a log chart, earlier cycles become visible and comparable. Long-term models such as the rainbow chart and the power law are drawn on log scales.
The choice of scale changes analysis. A trend line or pattern drawn on a log chart can break at a different point than the same line on a linear chart, and log charts visually compress recent large moves. Analysts should state which scale they use when citing a trend line.
Example
On a linear chart, bitcoin's rise from 1,000 to 20,000 dollars in 2017 looks like a tiny bump next to later cycles. On a log chart, it appears as large as any rally since.