I was doing some research on the Barbary Wars the other day, and ran across an interesting comment in the Naval Documents series put out in the 1930s. It's a letter to the Secretary of State from James Cathcart, from the port of Leghorn and dated July 4 1802. Talking about that port, Cathcart says:
"I have seen twenty-four sail of American vessels in this port at once last year, two-thirds of whom were unarmed."
So, out of 24 US merchantmen in Leghorn, 16 were unarmed! I know this is one time, one place observation, but it would be interesting to see how that compares to British merchantmen of the same period.