I'm playing as Morocco, and most of my provinces have a goods produced number of less than 1. Sometimes even around .30. I have some very valuable goods (ie gold, spices, salt, copper) that I would love to have more of, but I don't know how to increase the number produced. I thought the base was 1, and I don't see any negative modifiers.
If this is really Goods Produced (and not production income which could be influenced by an overseas location), then the only reason for such low numbers should be war exhaustion which applies a negative modifier (of -0.2/point) to Goods Produced (there are other negative modifiers when you're under siege, being blockaded, and such, but you'd have probably noticed and mentioned that). You say that you see no negative modifiers, but there must be some or the number shouldn't be this low.
To increase income, reduce your war exhaustion. You can also increase Goods Produced by raising your stability, but low stability shouldn't be why you currently have such low income.
Note that I haven't played since September, so this information is possibly not exactly correct for the current patch.