Speaking about print numbers, I remembered these pages from
The Asahi Shimbun newspaper with all One Piece print numbers from 1997 to 2014.
End of 1997: One Piece Volume 1 (24/12/1997) 300,000 copies.
End of 1998: 6,000,000 copies (6 Volumes).
End of 1999: 17,000,000 copies (11 Volumes). One Piece Anime started in October 1999.
End of 2000: 37,000,000 copies (16 Volumes). First print of new One Piece Volumes around 800,000 copies thanks to the Anime.
End of 2001: 54,000,000 copies (21 Volumes).
End of 2002: 73,000,000 copies (26 Volumes).
End of 2003: 90,000,000 copies (31 Volumes).
End of 2004: 99,000,000 copies (35 Volumes). First print of new One Piece Volumes went down for the first time.
End of 2005: 112,000,000 copies (39 Volumes). One Piece reached 100,000,000 copies in February 2005 with Volume 36 (I think Dragon Ball reached 100,000,000 copies after Manga ended, but I'm not sure).
End of 2006: 125,000,000 copies (44 Volumes).
End of 2007: 139,000,000 copies (48 Volumes).
End of 2008: 153,000,000 copies (52 Volumes).
End of 2009: 177,000,000 copies (56 Volumes).
End of 2010: 216,000,000 copies (60 Volumes). One Piece reached 200,000,000 copies in November 2010 with Volume 60.
End of 2011: 257,000,000 copies (64 Volumes).
End of 2012: 281,000,000 copies (68 Volumes).
End of 2013: 302,000,000 copies (72 Volumes). One Piece reached 300,000,000 copies in November 2013 with Volume 72.
End of 2014: 320,000,000 copies (76 Volumes).