Writing about web page http://ideas.repec.org/top/index.html
RePEc is a database for Economics papers and outputs, and citation analysis has been carried out, along with other measures, to provide rankings for items, series, authors, institutions and regions. This page lists these rankings and has links to information about how they were calculated.
It's a really great resource if you're looking to benchmark or compare one entity against another. RePEc's IDEAS offers a selection of different measures and rankings for each type of entity. Item rankings offered include one by simple citation count and others which are citation counts weighted by various factors, eg the impact factor of the citing publication (termed "recursive" by RePEc) or a discount for the age of the citation. A ranking by item downloads within RePEc is also included, and even by abstract viewings.
Series rankings include journals by impact factor, which is calculated based on RePEc's own data and is offered in varieties like those for items, including a weighted or recursive score based on the impact measures of the citing sources. I like the simple feature that it includes journals by their full title, which Web of Science's JCR impact factor listings do not: I am not so familiar with journal titles or their abbreviations that I find the JCR list easy to interpret!
Authors are only ranked if they are registered with RePEc and the top 10% appear on their summary table. Even if you're not in the top 10% it seems worthwhile registering because you can access data about your own publications. This must be so much more meaningful than looking up your own h-index on Web of Knowledge, in isolation. Even though you can look at the profiles of highly cited authors on Web of Knowledge, these won't all be people from within your own field and comparing rankings based on citation scores across different disciplines is not all that meaningful because citation practices vary across the disciplines.
RePEc seems to make it easy for authors to use bibliometrics and other measures in an intelligent and balanced manner and in that sense Economists seem to be very well provided for. I'm not a registered author so I can't see what goes into the updates or reports that authors can see, and I know that citations are scraped and parsed by software so I wonder how accurate the data is in the first place, but presumably as a registered author you can correct any errors.
All this is great for Economists and probably those in related disciplines, but I wonder what effect such specialisation of both data source and methodology is going to have on the use and impact of bibliometric measures? I'm sure others will have compared Web of Knowledge rankings with those of RePEc, so I'll have to investigate further!