Trend removal (or trend adjustments) try to separate long terms trends from shorter term fluctuations in data. Typically the long-term trend is estimated, often as a linear growth or decay and then subtracted from the data values. The term is usually applied to time series data, but can be appled equally to other forms of sequential data. Some transformations implicitly remove trend. For example taking successive differences of a time series (ti+1−ti) effectively removes any linear trend. Simlarly, taking successive ratios (ti+1/ti) removes exponential trend.
Used on pages 329, 330
Also known as de-trending, trend adjustments