1. One or more computer readable media having computer-executable instructions embodied thereon for performing a method for forecasting keyword search volume, comprising: providing one or more concept categories; constructing a category level seasonal variation pattern for each of the one or more concept categories, wherein seasonal variation refers to fluctuations in keyword search volume of one or more directly forecastable keywords included in the concept category based on trends that periodically repeat; identifying a seasonality of each of the one or more concept categories based on an associated category level seasonal variation pattern, assigning a non-directly forecastable keyword to a category selected from the one or more concept categories; and generating a forecast of keyword search volume for the non-directly forecastable keyword based on the seasonality of the assigned category, wherein the forecast is based on the category level seasonal variation pattern associated with the assigned category when the assigned category is identified as a seasonal category, and the forecast is based on a previous search volume associated with the assigned category when the assigned category is identified as a non-seasonal category.