I took the growth figures from 1945 through 2005 and use the past growth rates to predict the future rates and this is what I got...
By 2010 the growth rate will reach 0 and after that the Average Number of Publishers will start to go down. Their Average Number of Publishers should stop rising at about 6.6 million members and by 2025 they should be back to 5 million. It took them 122 years to reach 5 million publishers and it will only take 10 years to go back to 5 million publishers after they peak out at 6.6 million in 2010.
Year Average Publishers Percent Change1945 "127,478"
1946 "158,034" 19.34%
1947 "181,071" 12.72%
1948 "230,532" 21.46%
1949 "279,421" 17.50%
1950 "328,572" 14.96%
1951 "384,694" 14.59%
1952 "426,704" 9.85%
1953 "468,106" 8.84%
1954 "525,924" 10.99%
1955 "570,694" 7.84%
1956 "591,556" 3.53%
1957 "653,273" 9.45%
1958 "717,088" 8.90%
1959 "803,482" 10.75%
1960 "851,378" 5.63%
1961 "884,587" 3.75%
1962 "920,920" 3.95%
1963 "956,648" 3.73%
1964 "1,001,870" 4.51%
1965 "1,034,268" 3.13%
1966 "1,058,675" 2.31%
1967 "1,094,280" 3.25%
1968 "1,155,826" 5.32%
1969 "1,256,784" 8.03%
1970 "1,384,782" 9.24%
1971 "1,510,245" 8.31%
1972 "1,596,442" 5.40%
1973 "1,656,673" 3.64%
1974 "1,880,713" 11.91%
1975 "2,062,449" 8.81%
1976 "2,138,537" 3.56%
1977 "2,117,194" -1.01%
1978 "2,086,698" -1.46%
1979 "2,097,070" 0.49%
1980 "2,175,404" 3.60%
1981 "2,247,486" 3.21%
1982 "2,347,334" 4.25%
1983 "2,501,722" 6.17%
1984 "2,680,274" 6.66%
1985 "2,865,183" 6.45%
1986 "3,063,289" 6.47%
1987 "3,237,751" 5.39%
1988 "3,430,869" 5.63%
1989 "3,624,773" 5.35%
1990 "3,846,811" 5.77%
1991 "4,071,954" 5.53%
1992 "4,289,737" 5.08%
1993 "4,483,900" 4.33%
1994 "4,695,111" 4.50%
1995 "4,950,344" 5.16%
1996 "5,167,258" 4.20%
1997 "5,353,078" 3.47%
1998 "5,544,059" 3.44%
1999 "5,653,987" 1.94%
2000 "5,783,003" 2.23%
2001 "5,881,776" 1.68%
2002 "6,047,997" 2.75%
2003 "6,184,046" 2.20%
2004 "6,308,341" 1.97%
2005 "6,391,500" 1.30%
2006 "6,455,415" 1.00%
2007 "6,513,514" 0.90%
2008 "6,552,595" 0.60%
2009 "6,578,805" 0.40%
2010 "6,587,029" 0.13%
2011 "6,567,268" -0.30%
2012 "6,534,431" -0.50%
2013 "6,488,690" -0.70%
2014 "6,423,803" -1.00%
2015 "6,340,294" -1.30%
2016 "6,245,190" -1.50%
2017 "6,139,021" -1.70%
2018 "6,016,241" -2.00%
2019 "5,877,867" -2.30%
2020 "5,725,043" -2.60%
2021 "5,564,742" -2.80%
2022 "5,397,799" -3.00%
2023 "5,219,672" -3.30%
2024 "5,036,983" -3.50%