The demands they are a-changin’
针对时间趋势无法捕捉的不规则需求变动，提出一种指数方法将总需求变动分解为可预测和不可解释部分，并应用于养殖三文鱼市场，发现未知因素对需求影响不规则且贡献了近年全球需求增长的一半以上。
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.