what is seasonality 
seasonality refers to the predictable changes that occur over the course of a year to an economy or business it is not uncommon for certain times of the year to result in a drastic change in sales for companies within certain sectors for example holiday spending is often a major driver of full year revenue growth for companies within the retail sector the bottom linethe january barometer has demonstrated its staying power as a concept since it was first introduced more than 50 years ago the statistical debate about whether the indicator is truly a good predictor of the performance of the s p 500 index will likely continue for decades regardless the start of a new year always presents traders with a fresh opportunity to forecast what could happen over the months ahead and it doesn t take much of a stretch to expect that indicators such as the january barometer will continue being part of that discussion 