How many accounts can a CSM manage?

Many thanks to RD, a long-time blog reader, for this question.

The right answer is, “it depends.” And here are some observations:

• What are you expecting the CSMs to do with their accounts? Many vendors have entirely different programs, and ratios, for large accounts as compared to smaller accounts.
• At the high end, I see ratios of 1:7 to 1:10. This is for situations where the CSM is expected to build tight relationships within the account, including with the executives, hold regular meetings to discuss strategy (not just case reviews), and serve as the voice of their customers within the company.
• In rare cases, I’ve seen CSMs handle a single (huge!) account if it contributes a significant portion of the company revenue, has multiple divisions, etc.
• At the low end, I’ve seen ratios as high as 1:200. With that many accounts, the relationship with each account is much looser and consists mostly of canned communications, renewal notices, and ad-hoc retention actions. You cannot really be proactive with dozens or hundreds of accounts.

How do you plan your CSM:account ratio?