Queue abandonment happens when a customer leaves a queue, or decides not to join one at all, because the wait seems too long. The business loses a sale it had effectively already won. Leaving after joining is often called reneging, and not joining at all is called balking.
It is hard to see in POS data because the sale simply never appears. It can be estimated by comparing counts of people who enter a queue zone with the number of transactions, or by watching queue length and wait time through sensors, cameras or staff observation.
Cafés, QSR outlets, pharmacies and busy retail stores use it to decide when to open another till, bring in a floater or introduce self-service kiosks and mobile ordering. Tracking it by time of day shows which periods need extra support.
Pitfalls include judging only by average wait, which hides the peak when most customers walk away, and counting people who were never intending to buy. Estimates are approximate, so treat them as a guide. Counting stations at the queue entrance and the till, if available, give a firmer basis than guesswork. Consider the cost of extra staff against the sales likely to be recovered.
Reducing abandonment protects sales at the busiest and most valuable times.