What is F1000?: F1000 factors and rankings

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F1000 factors and rankings

F1000 has a unique system for ranking articles and has now extended this system to rank the journals they are published in.

When a Faculty Member evaluates an article in F1000, they rate the article 'Recommended', 'Must Read' or 'Exceptional' (equivalent to scores of 6, 8 or 10, respectively). We use these scores to calculate the F1000 Article Factors (FFa) for each individual article, from which we then generate F1000 Article Rankings. We also use the Article Factors to calculate F1000 Journal Factors and subsequently, F1000 Journal Rankings.

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F1000 article factors

The F1000 Article Factor (FFa) is calculated from the highest score awarded by a Faculty Member (FM) plus an increment for each additional score from other FMs (1, 2 or 3 for 'Recommended', 'Must Read' or 'Exceptional', respectively).

Rating	Value	Increment
Exceptional	10	3
Must Read	8	2
Recommended	6	1

For example, a single article that has been evaluated by three FMs, who scored it 'Recommended', 'Must Read' and 'Must Read', will have an FFa of 11:

8 (highest score 'Must Read') + 2 (increment for 'Must Read') + 1 (increment for 'Recommended') = 11.

The F1000 Article Factor is displayed next to the article citation on each record, and the individual scores next to the each individual evaluation.

F1000 article rankings

The more evaluations an article receives and the higher the scores, the higher its FFa and therefore its ranking.

All Time Top 10s and Current Top 10s are available for all F1000, by all Biology or Medicine Faculties, and by individual Faculty. We also publish Top 10 lists of Hidden Jewels that include only articles published in specialist journals that you might have missed in your general reading. Most Viewed lists enable you to see what your fellow readers are interested in. Current Top 10 lists are compiled daily and include articles evaluated within the preceding 14 days.

F1000 journal factors

F1000 Journal Factors (FFj) are calculated from individual Article Factors (FFa) that have accrued over a specific time period. We sum the individual FFas for a journal's articles, which we can represent by:

$\left ( \sum_{k=1}^N FFa(k) \right )$
Sum of Article Factors

for all evaluated articles k within the timeframe we're considering. We then calculate the percentage of research articles published in that journal that have been evaluated by F1000 Members, using figures obtained from PubMed:

$\left ( \frac{articles(F1000)}{articles(Pubmed)} \times 100 \right )$
Normalization Factor

We then normalize the sum of the FFas for each journal against the number of articles they publish each year:

$\left ( \sum_{k=1}^N FFa(k) \right ) \times \left ( \frac{articles(F1000)}{articles(Pubmed)} \times 100 \right )$

We find that this yields values spanning several orders of magnitude. So for the sake of ease of use and display, we apply a log scale:

$log_{10} \left \{ \left ( \sum_{k=1}^N FFa(k) \right ) \times \left ( \frac{articles(F1000)}{articles(Pubmed)} \times 100 \right ) + 1 \right \}$

Note that the "+1" is simply to ensure that low-scoring journals yield a positive value after taking the log₁₀.

And finally, we move the decimal point one place to the right (i.e. multiply by 10), again just to make the final FFj a readable number:

$FFj = log_{10} \left \{ \left ( \sum_{k=1}^N FFa(k) \right ) \times \left ( \frac{articles(F1000)}{articles(Pubmed)} \times 100 \right ) + 1 \right \} \times 10$

Figure 1: Journal Factor (FFj) equation

More simply, we can represent the full equation thus:

$FFj = log_{10} \left \{ \left ( Sum of Article Factors \right ) \times \left ( Normalization Factor \right ) + 1 \right \} \times 10$

Figure 2: Simplified Journal Factor (FFj) equation

F1000 journal rankings

Journal Rankings are available for across all the data in F1000, by all Biology or Medicine Faculties, and by individual Faculty and Section. This allows you not only to see where our Members think the best research is being published in each specialty, but also where best to publish your own research. Critically, you can trace each FFj back to the evaluations by F1000 Members who scored each article, so you can see exactly which articles have contributed to a journal's place in the rankings.

Although we only display FFjs to two decimal places, we calculate them to a precision of up to eight decimal places. We use this greater precision in determining the rankings. Higher precision FFjs are visible if you mouse over any FFj value.

Current Journal Rankings

Current Journal Rankings are calculated on the first day of each month and are the most up-to-date measure of a journal's performance in F1000. They take into account all evaluations published in F1000 over the preceding 12 months, regardless of the publication date of the article.

Provisional Annual Journal Rankings

Provisional Annual Journal Rankings are calculated at the beginning of July. They are based on every evaluated article that was published in the previous full calendar year. Although we receive 85% of evaluations within three months of publication of an article, this gives an extra three months for evaluations to accrue, reducing the disadvantage to articles published later in a year.

Final Annual Journal Rankings

Final Annual Journal Rankings are also calculated at the beginning of July. However, they are based on articles that were published in the last but one full calendar year. The 18-month time lag enables us to include 99% of potential evaluations for an article, even for those published towards the end of a calendar year.

For example, on 1st July 2012 we will publish:

2010 Final Annual Rankings

»Articles published in 2010 with the FFa calculated from evaluations on F1000 in 2010, 2011 and the first 6 months of 2012

2011 Provisional Annual Rankings

»Articles published in 2011 with the FFa calculated from evaluations on F1000 in 2011 and the first 6 months of 2012

Current Journal Rankings

»All articles, regardless of publication date, that received an evaluation between 1 July 2011 and 30 June 2012

Criteria for calculating Rankings:

For an article to be taken into account in the Journal Rankings it must:

»Have an associated PubMed ID
»Have a publication type of: Journal Article
»Not have a publication type of: Biography, Comment, Duplicate Publication, Editorial, Guideline, Historical Article, Interactive Tutorial, Interview, Lectures, Legal Cases, Letter, News, Newspaper Article, Patient Education Handout, Portraits, Practice Guideline, Retracted Publication, Retraction of Publication, or Review
»Not be retracted by the publisher.

For a journal to be included in the Journal Rankings it must:

»Have at least 24 articles published in PubMed in a given 12-month period
»Have at least 1 evaluation as per criteria above.