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Smooth operators such as time trends are often applied to deal with unidentified demand shifters. However, if unknown factors affect demand irregularly, a time trend fails to capture the variation. We present an index approach for estimating irregular demand shifts, decomposing total demand shifts into predicted and unexplained effects. This allows separating demand shifts caused by known factors like income and substitution effects from unknown impacts on demand. Our application on farmed salmon shows unknown factors impact demand irregularly both between regions and within regions over time. Unknowns contribute to more than half of global salmon demand growth in recent years.

A reliable growth function is a vital part of deriving the optimal harvesting strategy and production plan for any aquaculture operation. The range of environmental and biological conditions along the Norwegian coast suggests that the growth of farmed salmon will differ from one region to another. We estimate an aggregated regional growth function for three different regions in Norway using monthly data from 2005 to 2011. There is currently some variation for the grow-out period, and Atlantic salmon is raised between 16-24 months to reach weights of 2-8 kg. These results indicate that an increase in sea temperature positively affects the growth in the regions of Northern and Central Norway, while an increase in sea temperatures negatively affect the growth in the Southern region.

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