Table 3 Slope of linear regressions of annual cumulative proportions of WR for the major 6 countries. T & F Men 1920-1939 1950-1969 1970-1989 1990-2008 USA 0.005 0.0071 0.0027 0.0013 RUS 0.0033 0.0022 0.0003 ALL 0.0011 0.0003 0.0005 0 GDR 0.0015* - CHN 0.0002 0.0003 GBR 0.0002 0.0005* 0.0013 0.0002 T & Women USA 0.0007 0.0005 0.0022 0.0006 RUS 0.0002 0.0047 0.0041 0.0018 ALL 0.0031 0.0005 0.0005 0 GDR 0.0004 0.0071 - CHN 0.0002 0.0002 0.0009 GBR 0.0012 0.0004 0.0005* 0.0005* Swimming Men USA 0.0037 0.0075 0.0063 0.0031 RUS 0.0009 0.0012 0.0005 ALL 0.0007 0.0001 0.0007 0.0003* GDR 0.0007 0.0042 - CHN 0 0.0005 AUS 0.0002 0.0024 0.0007* 0.0022 Swimming Women USA 0.0043* 0.008 0.0041 0.0015 RUS 0.0006 0.0006 0 ALL 0.0007 0 0 0.0006* GDR 0.0008 0.0091 - CHN 0.0001 0.0012 AUS 0.0003* 0.0022 0.0010* 0.0017* P <0.001 for all the results except those indicated * T & F = Track & Field