When the leagues expanded, they brought several weaker teams into the league, allowing the incumbent teams to post better records. How much better? When did the expansion teams finally catch up? To try to answer these questions I looked at the combined record for the eight original franchises in each league. The totals are given in the table below. Totals below .500 are in red. Peak seasons are in bold green. Please e-mail me if you have any constructive comments.
Dave Studenmund has made some observations about the trends.
Note that the 8 original NL franchises rose to a record high
performance in 2004 (5 of the top 6 records in the NL, 6 of the 8 were
above .500. Led by large drops by the Dodgers and Giants, 7 of the 8
did worse in 2005 than in 2004, dropping their cumulative record below
.500, where it has stayed the last several years, the longest such run
for any single league - though the 16 franchises combined were under
.500 for 5 consecutive years 1985-1989.
Leg. Year W L Pct. Leg. Year W L Pct. Year W L Pct. AL 1960 616 616 .500 NL 1960 616 616 .500 Total 1960 1232 1232 .500 AL 1961 676 616 .523 NL 1961 616 616 .500 Total 1961 1292 1232 .512 AL 1962 662 631 .512 NL 1962 706 594 .543 Total 1962 1368 1225 .528 AL 1963 682 611 .527 NL 1963 693 603 .535 Total 1963 1375 1214 .531 AL 1964 666 630 .514 NL 1964 691 605 .533 Total 1964 1357 1235 .524 AL 1965 665 631 .513 NL 1965 694 600 .536 Total 1965 1359 1231 .525 AL 1966 654 635 .507 NL 1966 670 623 .518 Total 1966 1324 1258 .513 AL 1967 648 646 .501 NL 1967 679 615 .525 Total 1967 1327 1261 .513 AL 1968 677 618 .523 NL 1968 665 631 .513 Total 1968 1342 1249 .518 AL 1969 681 613 .526 NL 1969 687 609 .530 Total 1969 1368 1222 .528 AL 1970 686 610 .529 NL 1970 673 621 .520 Total 1970 1359 1231 .525 AL 1971 673 616 .522 NL 1971 677 619 .522 Total 1971 1350 1235 .522 AL 1972 659 580 .532 NL 1972 634 606 .511 Total 1972 1293 1186 .522 AL 1973 674 622 .520 NL 1973 667 626 .516 Total 1973 1341 1248 .518 AL 1974 665 629 .514 NL 1974 680 615 .525 Total 1974 1345 1244 .520 AL 1975 653 626 .511 NL 1975 678 615 .524 Total 1975 1331 1241 .517 AL 1976 659 628 .512 NL 1976 678 618 .523 Total 1976 1337 1246 .518 AL 1977 676 615 .524 NL 1977 683 613 .527 Total 1977 1359 1228 .525 AL 1978 657 636 .508 NL 1978 671 623 .519 Total 1978 1328 1259 .513 AL 1979 657 628 .511 NL 1979 654 639 .506 Total 1979 1311 1267 .509 AL 1980 679 610 .527 NL 1980 649 646 .501 Total 1980 1328 1256 .514 AL 1981 448 408 .523 NL 1981 437 412 .515 Total 1981 885 820 .519 AL 1982 638 658 .492 NL 1982 663 633 .512 Total 1982 1301 1291 .502 AL 1983 672 624 .519 NL 1983 656 640 .506 Total 1983 1328 1264 .512 AL 1984 669 627 .516 NL 1984 631 664 .487 Total 1984 1300 1291 .502 AL 1985 644 649 .498 NL 1985 622 671 .481 Total 1985 1266 1320 .490 AL 1986 648 647 .500 NL 1986 613 678 .475 Total 1986 1261 1325 .488 AL 1987 636 660 .491 NL 1987 647 647 .500 Total 1987 1283 1307 .495 AL 1988 660 633 .510 NL 1988 621 668 .482 Total 1988 1281 1301 .496 AL 1989 624 670 .482 NL 1989 627 665 .485 Total 1989 1251 1335 .484 AL 1990 658 637 .508 NL 1990 646 650 .498 Total 1990 1304 1287 .503 AL 1991 629 667 .485 NL 1991 673 621 .520 Total 1991 1302 1288 .503 AL 1992 661 635 .510 NL 1992 650 646 .502 Total 1992 1311 1281 .506 AL 1993 647 649 .499 NL 1993 704 592 .543 Total 1993 1351 1241 .521 AL 1994 477 431 .525 NL 1994 456 457 .499 Total 1994 933 888 .512 AL 1995 587 565 .510 NL 1995 582 569 .506 Total 1995 1169 1134 .508 AL 1996 658 637 .508 NL 1996 639 657 .493 Total 1996 1297 1294 .501 AL 1997 650 644 .502 NL 1997 643 653 .496 Total 1997 1293 1297 .499 AL 1998 663 633 .512 NL 1998 672 626 .518 Total 1998 1335 1259 .515 AL 1999 661 631 .512 NL 1999 659 636 .509 Total 1999 1320 1264 .510 AL 2000 670 624 .518 NL 2000 657 639 .507 Total 2000 1327 1263 .512 AL 2001 667 625 .516 NL 2001 659 637 .508 Total 2001 1326 1262 .512 AL 2002 670 623 .518 NL 2002 682 609 .528 Total 2002 1352 1232 .523 AL 2003 650 646 .502 NL 2003 689 606 .532 Total 2003 1389 1252 .517 AL 2004 695 601 .536 NL 2004 708 587 .547 Total 2004 1403 1180 .542 AL 2005 698 598 .539 NL 2005 643 653 .496 Total 2005 1341 1251 .517 AL 2006 705 591 .544 NL 2006 624 670 .482 Total 2006 1329 1261 .513 AL 2007 670 626 .517 NL 2007 629 667 .485 Total 2007 1299 1293 .501 AL 2008 659 637 .508 NL 2008 644 651 .497 Total 2008 1303 1288 .503 AL 2009 654 644 .504 NL 2009 676 618 .522 Total 2009 1330 1262 .513 AL 2010 663 633 .512 NL 2010 669 627 .516 Total 2010 1332 1260 .514 AL 2011 647 649 .499 NL 2011 671 624 .518 Total 2011 1318 1273 .509 AL 2012 658 638 .508 NL 2012 680 607 .528 Total 2012 1338 1245 .518Here's the graph of the won-lost percentages.
