Comma before “respectively”?

That's right.

IMO "respectively" is not essential, but is used as a formality.

I can't believe that everyone is missing the point on this one. The comma should be a semi-colon as the separation is being used for a list. The other basic reason that a semicolon is needed is that it is a longer break and gives the reader a chance to process the info given and then to anticipate the complicated relationship implied by the term "respectively".

Completely serious, koam. Was there something I missed. I always was taught that semicolons are used in lists. That's what I was trying to say.

I do have some problems with my brain and face because of birth defects, andd so I don't apreciate the "troll" comment.

@Brock ... How would you even write that with a semicolon? No semicolon, colon, or comma needed in this example.

The only thing missing hasn't anything to do with layout of the sentence but some units would be nice ... 18 gal? 200 L?

essential: nonsense
comma: optional

koam: assertions
sigurd: supported assertions

GWU: correct.

What on earth are you on about, Brock? Unless you're joking and I missed the humour. haha. There is no list there...

KWM are you serious? The fishing term is TRAWLING. Trolls were mythical norse beings that were wicked and mischievous. I do hope you're being ironic.

Respectively is required to show monthly is 18 and yearly is 200. Informally you can do without it but when comparing figures I think it should be included. Anwulf was correct, only use a comma if your sentence is getting unwieldy and it's required for clarity.

porsche et al are of course right about trolling being a type of fishing (although I confess I had to check a dictionary, as this seems to be more of a North American usage). Hence the meaning of to search for something - "politicians trolling for votes", as well as the newer meaning that KWM explained (also given at Oxford Online).

Incidentally, there is another British meaning of "troll" as a verb- "walk, stroll", probably from Polari, a kind of cant slang, some of whose word were made famous by Kenneth Williams and Hugh Paddick on "Round the Horne". "Look who's trolling in!"

http://en.wikipedia.org/wiki/Polari

Google site searches of both American and British newspapers would suggest that use of comma or no comma before "respectively" is fairly evenly divided.

One editing blog suggests it's context specific - "If the sentence is long and has many parameters, then use the comma for clarity. If not, the comma may be omitted". And he adds there is no difference between AmE and BrE here. Seems a sensible approach to me.

http://blog.editage.com/taxonomy/term/350#.UXWZdkrQWM4

I stand corrected! I have never heard of trolling as a fishing term and I've worked with fishermen!

No no no!

The best way to convey this is as follows:
Sewer projection flow monthly: 18
Sewer projection flow yearly: 200

Respectfully,
GKB

Simples!

One use of the comma in English is to indicate a slight pause; so there is a difference between "Roses are red and violets are blue" and "Roses are red, and violets are blue" - the latter has a slight pause before "and".
In the same way I would suggest the comma before "respectively" marks a slight pause.
One can in fact say it either way.
The only corollary to this is that in recent years commas have been dying out - I use them only where necessary these days to make the meaning clear or to clearly indicate a slight pause.

I'll bite.

BrockawayBaby, a semicolon should NOT be used, as there not a list. There are only two items. Even if there was a list, there would not be a semicolon before "respectively" anyway. "Respectively" is a comment on the order of "18" and "200," not part of the items. Your solution is grammatically incorrect.

To the chair of the governors and governors, respectively,
(is this the right way to open a letter?)