Figure 1 shows the difference most clearly in terms of pigs weaned per mated female per year. The differences are relatively consistent across quarters, though greatest in the fourth quarter. The mean difference, of approximately 1.6 pigs per year, can be described in terms of differences in constituent reproductive output. However, it is also useful to notice that seasonal differences are accentuated in the American herds as well. The letters above the American quarters designates which quarters have different levels of output. We see that the first and third quarters are approximately the same but that the second quarter is higher and the fourth quarter is considerably lower (p<.05). This change in productivity reflects overall throughput trends as well.