Here we go through several ideas on how you can rank and position the top consulting companies. We are employing an extremely helpful strategic tool - multi-dimensional strategic choices or strategic dimensions. Ranking means applying one or several criteria or dimensions and then deciding how the list of companies looks from the top to the bottom. More information on how the dimensions method is applied to the other areas of strategic consulting can be found here.
There are several standard and some non-standard strategic dimensions that are usually applied to rank consulting companies.
First, rank companies by geography or their geographical distribution. Place companies with the most countries they are working at the top and then work down the list. Basically, at the top you get the most spread around the world companies. So you can understand which companies are truly multinational and global in their outreach.
The second standard dimension is products. Go through the websites of the strategic companies of interest and check the products that they offer. Decide what company offers the most products, then the one that offers second-most, etc. In this way, you can understand which companies are more diverse in their product line. In other words, which companies help their customers within more areas or within more functional questions.
While this is a standard dimension in the strategic analysis it is quite difficult to gather reliable data on the number of clients. Normally consulting companies protect these data and clients mostly like to have confidentiality. Nevertheless, with some effort and estimation, this type of rankings can also be created.
There is the so-called prestige characteristic. This is a more specific dimension for consulting companies. Prestige is rather a subjective way of ranking companies. Hence it should be used with caution. It is also crucial also check the methodology that is applied. Mostly this ranking is created with polling some kind of a representative group: like 10,000 respondents employed at the top and middle management in consulting.
Other non-standard dimensions that are usually used in the rankings are quantitative metrics. They are based on the financial or rather numerical results that companies show.
As it has been shown, there are many ways to rank consulting companies. Furthermore, a great idea would be to combine several approaches (you don't need to combine too many of them). Just go with two to five in order to cover the major aspects of the companies' performance. For example, you could rank firms by geography, the number of employees, prestige, and revenue growth. These metrics would be covering the companies' global reach, their capacity, brand power, as well as their efficiency.
Finally, many examples of these rankings exist. Find them on the internet, choose the most relevant, and combine to get a multi-dimensional view.