On a state-wide basis, the percentage of recycled fiber contained in directory stock used by all directory publishers shall be in accordance with the following schedule: For the year ending December 31, 1995, ten per cent or more; for the year ending December 31, 1996, fifteen per cent or more; for the year ending December 31, 1997, twenty per cent or more; for the year ending December 31, 1998, twenty-five per cent or more; for the year ending December 31, 1999, thirty per cent or more; for the year ending December 31, 2000, thirty-five per cent or more; and thereafter, forty per cent or more.