Extract from the "model":

                $yearsBetween = $comparisonItems->created_at->diffInYears(Carbon::now());
                if ($yearsBetween <=1) {
                    $multiplier = 1.08;
                } else if ($yearsBetween <= 2) {
                    $multiplier = 1.12;
                } else if ($yearsBetween <= 3) {
                    $multiplier = 1.15;
                } else if ($yearsBetween <= 4) {
                    $multiplier = 1.22;
                } else if ($yearsBetween <= 5) {
                    $multiplier = 1.37;
                } else {
                    $multiplier = 1.41;
                }

The thing is, customers were happy with the result and, as far as I know, still are. Internally it was always called the random number generator.