I think this decline is related to two things:

[kexej28769@nongnue]

As local search becomes more complex, additional signals are added to the algorithm and this reduces the value that is used to provide referrals. There are more things to optimize in local search these days.
As local search becomes more widely adopted, more businesses are perpetuating and building their referrals, and thus referrals become less of a competitive differentiator than they were in the past.
Yes, we’re seeing the importance of citations decline usa number data after year, but that doesn’t mean you don’t need them. Quite the opposite, really. If you don’t have them, you’re going to have a hard time. Google looks at your citations to help it understand how prominent your business is. A well-established and popular business should be present on the most important business directories in their industry, and if it’s not, it could be a signal of low importance to Google.

The good news is that citations are one of the easiest things to check for your local search listing. There are dozens of services and tools to help you get your business listed and accurate for just a few hundred dollars. Here’s what I recommend:

Make sure your business is listed, accurate, complete, and free of duplication on the top 10-15 most important sites in your industry (including primary data aggregators and industry/city specific sites).
Create citations on the next top 30 to 50 sites (but don't worry about duplicates and inconsistencies).
Google has become much more aware of citation consistency than it was in the past. People worry about it more than they need to. Incorrect or duplicate listings on a non-profit business listing site will not negatively impact your ranking potential.