Seasonality of demand is the regular fluctuation of interest in a product or service over the year. Most companies sense it intuitively but plan their marketing evenly, leaving money on the table in strong months and wasting it in weak ones. It can be measured quickly: compare revenue and enquiries by month over the last two to three years and supplement it with the trend in search volume for key topics. It's important to distinguish the season of interest from the season of purchase – for more expensive services, people gather information weeks to months before deciding, so an awareness-building campaign has to run earlier than a performance one. Use the off-season for what you can't get to at the peak: content, technical improvements to the website, the email database and testing. Reflect seasonality in cashflow too, not just in the campaign calendar.
See also: Company marketing budget, KPIs for a marketer, In-house marketer vs agency.
