Stationarity
Stationarity is a statistical property where a time series has a constant mean, variance, and autocorrelation over time. Financial time series, such as asset prices, are notoriously non-stationary, meaning their statistical properties change frequently.
This poses a significant challenge for predictive modeling, as most standard statistical methods assume stationarity. In the crypto market, prices are subject to trends, shocks, and volatility regimes that constantly break stationarity.
To handle this, traders often transform the data into stationary forms, such as returns or log-returns, or use models that are designed to adapt to non-stationary environments. Failing to address non-stationarity is a primary reason why models fail to generalize; they assume a stable world that does not exist.