I'm not that familiar with the "smart" goal system but I'll try and give it a go if it makes you understand it easier. There has been no percentage of posts that have been posted that was expected to be curbed. Specific goals can only be measured after a few months and not really foreseen before. It would be nice to have these statistics released at the time of reviewing the system though.
Normally the amount of new registrations would be accessible here
https://bitcointalk.org/index.php?action=statsbut I think this is currently disabled until further notice so it might be best to keep on checking that.
Some interesting data since the introduction of the merit system can be found here:
https://bitcointalksearch.org/topic/m.39521119That has some pretty indepth statistics on a few things that you might find interesting
Specific:
The merit system was introduced to specifically target those that are ranking up without contributing much to the forum in terms of posts. Therefore encouraging members to make more constructive posts. It specifically rewards those that make quality posts by allowing them to gain merit points and rank up. If a member does not make quality posts then they will not rank up. The idea behind this is to reduce the amount of users posting useless content and start actiely looking to make quality posts in order to rank up to access certain benefits of the forum like the bounties and signature campaigns which require you to be a certain rank but also the benefits that come with higher ranks such as avatars.
Measurable?
It's measurable by the amount of merits that a user receives and the amount of signal to noise ratio. A great way that this is measurable is by looking at a specific members merit received. If they have not received any merit at all or very little this normally shows that this user is not making quality posts. Moderators would be able to measure this too by looking at the amount of reports that they have received since the introduction of the merit system and comparing from before.
Achievable?
Well the goal has already been achieved. Its reduced the amount of people that are ranking up. However it hasn't reduced the amount of spam enough. It may have an impact of the amount of spam thats being posted but it certainly was not a complete solution to it. Especially since most bounties dont restrict who can join them.
Relevant?
Of course its relevant to the forum. The community including myself are getting sick and tired of the spam that Bitcointalk is covered in right now. So it was in everyone's interest to introduce a system like the merit system which is relevant to the spam issues right now.
Time bound?
The merit system is permanent and will not be removed so it is not time bound. However when reviewing the merit system it is probably wise to allow sufficient time for new merit sources to be added and a cooling down period after the initial panic of the merit system being introduced.
I would say a review 6 months in and a year later would be the best time to review the system and whether its doing what it was suppose to do and make any changes to it if necessary.