| Year | Jan. | Feb. | Mar. | Apr. | May | Jun. | Jul. | ||||
| 1,000 Head | |||||||||||
| 1963 | 12,183 | 11,398 | 13,641 | 14,424 | 15,763 | 14,581 | 13,438 | ||||
| 1968 | 16,706 | 15,793 | 17,659 | 17,836 | 18,824 | 17,550 | 17,617 | ||||
| 1973 | 19,944 | 17,434 | 20,831 | 21,175 | 21,699 | 20,216 | 19,298 | ||||
| 1978 | 21,742 | 19,630 | 22,991 | 23,365 | 24,496 | 23,410 | 22,380 | ||||
| 1983 | 26,902 | 24,275 | 28,239 | 28,206 | 28,335 | 27,445 | 27,197 | ||||
| 1988 | 30,033 | 27,211 | 30,116 | 29,546 | 30,272 | 29,748 | 29,951 | ||||
| 1989 | 30,917 | 28,019 | 32,069 | 32,256 | 33,729 | 32,862 | 32,946 | ||||
| 1990 | 31,958 | 29,746 | 33,977 | 35,073 | 36,123 | 36,020 | 35,846 | ||||
| 1991 | 37,615 | 33,432 | 38,209 | 37,649 | 39,316 | 38,652 | 38,320 | ||||
| 1992 | 40,202 | 37,167 | 39,899 | 39,713 | 41,510 | 40,842 | 41,887 | ||||
| 1993 | 42,645 | 38,806 | 44,826 | 43,714 | 46,261 | 46,058 | 46,718 | ||||
| 1994 | 49,204 | 43,932 | 50,869 | 50,611 | 54,036 | 53,341 | 53,208 | ||||
| 1995 | 55,842 | 49,284 | 54,678 | 53,652 | 56,022 | 54,213 | 55,043 | ||||
| 1996 | 56,472 | 52,653 | 55,847 | 56,207 | 59,292 | 57,826 | 58,397 | ||||
| 1997 | 61,954 | 55,756 | 63,943 | 62,728 | 65,266 | 62,375 | 62,892 | ||||
| 1998 | 62,878 | 57,204 | 64,959 | 63,460 | 65,139 | 63,174 | 64,000 | ||||
| Year | Aug. | Sep. | Oct. | Nov. | Dec. | Total | |||||
| 1,000 Head | |||||||||||
| 1963 | 13,090 | 11,512 | 13,108 | 13,943 | 13,904 | 160,985 | |||||
| 1968 | 17,497 | 15,599 | 16,242 | 16,127 | 16,433 | 203,883 | |||||
| 1973 | 20,078 | 18,416 | 18,680 | 19,113 | 19,878 | 236,762 | |||||
| 1978 | 21,450 | 20,533 | 20,954 | 20,072 | 22,030 | 263,053 | |||||
| 1983 | 25,321 | 24,275 | 24,174 | 23,457 | 25,934 | 313,760 | |||||
| 1988 | 30,495 | 29,163 | 28,985 | 27,677 | 31,064 | 354,261 | |||||
| 1989 | 32,591 | 31,597 | 30,572 | 29,766 | 33,181 | 380,505 | |||||
| 1990 | 35,370 | 33,194 | 33,058 | 30,974 | 37,473 | 408,812 | |||||
| 1991 | 28,231 | 37,503 | 37,332 | 36,413 | 39,955 | 452,627 | |||||
| 1992 | 41,635 | 41,080 | 40,528 | 37,955 | 42,883 | 485,301 | |||||
| 1993 | 45,720 | 44,620 | 44,482 | 43,806 | 47,956 | 535,612 | |||||
| 1994 | 53,413 | 52,506 | 52,310 | 49,476 | 55,408 | 618,314 | |||||
| 1995 | 54,368 | 52,411 | 52,641 | 50,646 | 56,853 | 645,653 | |||||
| 1996 | 58,548 | 57,065 | 57,890 | 54,273 | 61,145 | 685,615 | |||||
| 1997 | 60,829 | 59,411 | 61,095 | 57,879 | 62,068 | 736,196 | |||||
| 1998 | 63,382 | 62,095 | |||||||||