What does “much” add to the meaning of “How 'much' common were these crimes?”

The dictionary I consulted says that how much is used for asking or saying what the amount of something is:

(1) How much common were these crimes?

(2) How common were these crimes?

But, after reading (1) and (2) I don't still understand:

• How are they different?

• What is "the amount of something" to which how much refers in case (1)?

• The main difference is that (1) isn't correct English and (2) is. – Nigel Harper Jun 17 '13 at 22:25
• @Nigel, if (1) is not correct, how the concept of "commonness" can be quantified? – user114 Jun 17 '13 at 22:36
• Asking "How common is x" is enough to get an answer in terms of commonness - you don't need any more than that. – Nigel Harper Jun 17 '13 at 23:10
• How much ADJECTIVE is not idiomatic English. May we ask where you found this? – StoneyB on hiatus Jun 18 '13 at 0:57
• @Carlo_R. My written Italian has always been my Achilles heel, thank you for correcting me. (Lets hope for me, Italian language & Usage becomes reality!) – Mari-Lou A Jun 19 '13 at 18:55

How carries the sense of measure—of quantity, amount or degree—in itself, and takes an adjective or adverb to define what is to be measured:

How quickly did he run? ... you are asking for the measure of quickness, a speed.
How much money did he have? ... you are asking for the measure of muchness, an amount.
How many hamburgers can he eat? ... you are asking for the measure of manyness, a number.
How big is his house? ... you are asking for the measure of bigness, a size.

So when you ask "How common", there is no need for another adjective to specify that you are asking for a measure of commonness. That's what How? means, all by itself.

Consequently, How much common is not idiomatic English.

• Neat examples! I really like "muchness" and "manyness" there! It's not often you need words like that though (my browser spellchecker is unhappy about the latter! :) – FumbleFingers Reinstate Monica Jun 18 '13 at 3:05
• @FumbleFingers The credit is Carlo_R's: he set it up in his comment "how the concept of commonness can be quantified". – StoneyB on hiatus Jun 18 '13 at 3:40
• It might be worth noting that how can mean either to what degree, or in what way. Those two senses aren't always completely distinct - "How difficult can walking and chewing gum be?" would normally mean much the same as "How can walking and chewing gum be difficult?". But there is likely to be a difference in meaning between "How common is immortality?" and "How is immortality common?" (the first version asks to what degree, the second in what way). – FumbleFingers Reinstate Monica Jun 18 '13 at 14:14