From the first survey (1986) to the 10th survey (1995), books of both official and commercial publications were examined. From the 11th survey, it was decided that a survey on commercial publications should be conducted every four years, as the 10th survey showed that almost eight out of ten (79.3%) commercial publications used acid-free paper. The emphasis of the survey was shifted to books and periodicals of the government publications. The result of the 17th survey (2003) showed steadily high use rate of acid-free paper which was 93.8% on books and 86.2% on periodicals of the commercial publications.

1. Objects and method of the survey
The survey on books was done on 3.5% (302 volumes) of central government publications and 3.5% (234 volumes) of local government publications picked at random from 15,313 volumes which had been acquired and cataloged by the NDL by September 13, 2005, of all publications issued in 2004. For periodicals, 3.2% (152 titles) of central government publications and 3.2% (339 titles) of local government publications were picked at random from 15,355 titles which was regulary acquired as of September 13, 2005, and from each title, one issue published in 2004 was examined. 
Like the previous survey, publications of central government and local government were picked at random at the same rate to maintain unity of the condition of the survey. From these items, 412 books and 360 periodicals excluding coated paper materials and materials in use were examined by using Nikken Chemical laboratory's pen-style indicator.
As before, coated paper was excluded from the survey. Coated paper cannot be surveyed by this method as one or both sides of coated paper is covered with a clay coating. Of all the objects in this survey, 119 books and 79 periodicals, a total of 198 volumes, were coated paper materials. This is 19.3% of all surveyed objects (536 books and 491 periodicals), increase of 2.2 points from 17.1% of the previous survey.
A survey on recycled paper which was started from the 12th survey (1997) was also conducted. The survey was done by checking marks or descriptions indicating recycled paper use near the foreword or colophon of the materials.

2. Results

Table 1  Result (All)

The result of the survey is round up in Table 1. The use rate of acid-free paper on all materials was 93.8%, an increase of 2.4 points from the previous survey. All the material groups exceeded 90% for the first time since the first survey. Chart 1 shows the rate of acid-free paper used in books and periodicals over the last five years. The use rate of acid-free paper in local government publications used to exceed that of central government publications. According to the result of the previous survey, the use rate of acid-free paper on central government books exceeded those of local governments, and in the present survey, both books and periodicals of central government exceeded the local government rate. 

Chart 1

Recycled paper
The survey on recycled paper was done on 970 volumes of acid-free paper, acid paper and also coated paper. The rate of recycled paper was 22.0%, 213 volumes (of those, 52 volumes use coated paper). As there is no standard for recycled paper the survey was done by checking marks or descriptions of recycled paper use. Therefore the actual use rate of recycled paper may be higher than the result of this survey shows.
 

Table 2
The rate and amount of acid-free paper in the recycled paper 
(coated paper excluded)

NB: the numbers show volumes.

Conclusion
Judging by the results obtained, the use of acid-free paper on governmental publications seems to be well established. From now on, a survey on offcial publications will be conducted every four years, the same interval as the survey on commercial publications. The next survey will be done in FY2007 for commercial publications and in FY2009 for offical publications.