Life Science's Average Publishable Unit (APU) Has Increased over the Past Two Decades.

Area of Science:

• Biological Sciences
• Scientific Literature Analysis
• Bibliometrics

Background:

• Quantitative analysis of scientific literature is crucial for understanding the evolution and current state of science.
• The density of biological literature has not been systematically assessed over extended periods.

Purpose of the Study:

• To quantitatively analyze the changes in the size and complexity of biological research articles over two decades (1993-2013).
• To assess trends in data presentation, including figures, tables, and supplemental materials.
• To investigate the correlation between article metrics and journal Impact Factor (IF).

Main Methods:

• Analysis of 1464 research articles from ten biological science journals across 1993, 2003, and 2013.
• Scoring of data items (tables, figures), figure density (panels per figure - PPF), authors, pages, and references per publication.
• Calculation of the Average Publishable Unit (APU) to represent article size and complexity.

Main Results:

• The average number of data items per article increased from approximately 7 in 1993 to 14 in 2013.
• The average figure density (PPF) increased from 2 to 4 per article.
• Supplemental material constituted up to 80% of data items by 2013, significantly contributing to the increase in APU size.
• Average authors per publication increased from 5 to 8.
• Article metrics like data items, figure density, and author count correlated with journal IF.

Conclusions:

• The Average Publishable Unit (APU) in biological sciences has doubled over the past two decades.
• The rise of supplemental materials is a key driver of increased publication density.
• These trends have significant implications for the value, economics, and mechanisms of scientific communication.