Do the segments move gradually or in a big jump each year?
Segments move in monthly steps across the perceptual map.
This has consequences for demand, especially with products that are about to fail the positioning rough cut. If you look at one of the Segment Analyses in the Courier, you will often see products that made a small number of sales during the year, but have "December Customer Survey" scores of zero. These products passed the rough cut early in the year, but by December they were outside the outer limits.