That's because you're looking for a too-specific name. Amongst other things, in statistics and economics, this is one of the classical decomposition methods of time-series analysis, alongside multiplicative (a.k.a. product), log-additive, and pseudo-additive decomposition, and it is usually called simply additive decomposition. The people who tagged this "too technical" might be interested in the For Dummies explanation of this, which can be found on pages 245–247 of ISBN 9781118940013. A slightly more extensive treatment can be found on pages 93–95 of ISBN 9780521565882. This is a very narrow and specialized explanation of a general thing. Uncle G (talk) 21:06, 15 May 2016 (UTC)[reply]
