"Sale trajectory" refers to the path or direction a product's sales take over time. It helps determine if the sales are increasing, decreasing, or remaining stable. Full definition
It may result in a slow sales trajectory, but you've done what you need to do. (realtormag.realtor.org)
Entering 2014 we also anticipate Toronto maintaining its current upward sales trajectory.» (remonline.com)
Based on the current sales trajectory, it seems unlikely the Nintendo 3DS will top 25 million units in Japan alone, though it should be able to reach 24 million units sometime next year. (perfectly-nintendo.com)