Non-Open Access and Its Adverse Impact on Molecules

In 2005 and 2006 papers were published in MDPI journals in both non-Open Access (non-OA) and Open Access (OA) form [1,2]. In 2005, 70 papers (just under 50% of the total) were published in the password protected (non-Open Access) area of Molecules. Not undexpectedly, this reduced number of Open Access papers had a significant influence on the impact factor of Molecules, which was reduced from 1.113 in 2005 to 0.841 in 2006. According to the methods used in calculating impact factors, the number of papers published in 2005 and the number of citations were used in the calculation of the 2006 impact factor. The statistical data for non-OA and OA are presented in Table 1.

Table 1. Open Access (OA) and non-Open Access (non-OA) papers published in Molecules in 2005 [3].

	Number of papers 1	Number of citations 2	Average citation
Non-OA 3	70	43	0.614
OA	74	90	1.216

¹ Only research papers and review papers are counted. Other materials such as editorials, are not included. ² Up to 13 July 2007, according to Web of Sciences. ³ By April 2007, all the non-OA papers were changed to Open Access.

Table 1. Open Access (OA) and non-Open Access (non-OA) papers published in Molecules in 2005 [3].

	Number of papers 1	Number of citations 2	Average citation
Non-OA 3	70	43	0.614
OA	74	90	1.216

¹ Only research papers and review papers are counted. Other materials such as editorials, are not included. ² Up to 13 July 2007, according to Web of Sciences. ³ By April 2007, all the non-OA papers were changed to Open Access.

Like Molecules, in 2005 another MDPI journal, International Journal of Molecular Sciences, also published a significant percentage of papers in its password protected (non-Open Access) area. The impact factor of International Journal of Molecular Sciences was also reduced from 1.467 in 2005 to 0.679 in 2006. The statistical data for non-OA and OA are presented in Table 2.

As shown in Table 1 and Table 2, the non-Open Access papers and their obviously lower citation numbers appear to be the main reason behind the reduced impact factors of these two journals, where almost half of the papers published were in non-OA form.

Table 2. Open Access (OA) and non-Open Access (non-OA) papers published in International Journal of Molecular Sciences in 2005 [3].

	Number of papers 1	Number of citations 2	Average citation
Non-OA 3	11	5	0.455
OA	13	19	1.462

¹ Only research papers and review papers are counted. Other materials such as editorials, are not included. ² Up to 13 July 2007, according to Web of Sciences. ³ By April 2007, all the non-OA papers were changed to Open Access.

Table 2. Open Access (OA) and non-Open Access (non-OA) papers published in International Journal of Molecular Sciences in 2005 [3].

	Number of papers 1	Number of citations 2	Average citation
Non-OA 3	11	5	0.455
OA	13	19	1.462

¹ Only research papers and review papers are counted. Other materials such as editorials, are not included. ² Up to 13 July 2007, according to Web of Sciences. ³ By April 2007, all the non-OA papers were changed to Open Access.

As a contrast, the MDPI journal Sensors (http://www.mdpi.org/sensors/) published only a very small number of non-Open Access papers in 2005, and its impact factor increased slightly from 1.208 in 2005 to 1.373 in 2006.

Since April 2007, we have granted full Open Access to all the papers published in all MDPI journals in 2005 and 2006, and in 2007, we have published papers exclusively in Open Access form. We expect this will be reflected in an increase in impact factors come the next evaluation.

As always, we welcome our reader’s opinions on these matters [4]. Messages with a suitable Subject header should be sent to lin@mdpi.org.