Another approach is to use a historical analogy. For example, the manufacturer of HDTV might assume that the number of consumers willing to adopt high definition TV will be similar to the adoption rate for Color TV. To support this type of analysis, data for household penetration of TV, Radio, PCs, and other communications technologies is readily available from government statistics departments. Finding useful analogies can be challenging because every market is unique. However, analogous product adoption and growth rates can provide the analyst with benchmark estimates, and can be used to cross-validate other methods that might be used to forecast sales or market size.