Business and Personal Finance Dictionary

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• AUTOREGRESSIVE CONDITIONAL HETEROSKEDASTICITY (ARCH)
  
  A nonlinear stochastic process, where the variance is time-varying, and a function of the past variance. ARCH processes have frequency distributions which have high peaks at the mean and fat-tails, much like fractal distributions. The ARCH model was invented by Robert Engle. The Generalized ARCH (GARCH) model is the most widely used and was pioneered by Tim Bollerslev. See: Fractal Distributions.
  
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