Similar use of "auf" and "an"

Question

On articles about the recent decline in oil prices and OPEC, I read two sentences from two different sources online:

1. Der Preisverfall am Ölmarkt setzt sich fort. Source: Deutsche Welle (DW)
2. Preisverfall auf den Märkten. Source: SpiegelOnline

I would translate the DW sentence as "The price decline in the oil market continues." and the SpiegelOnline one as "Price decline in the markets".

Is there any difference in using auf vs an? The only reason I could think of is that sich fortsetzen might require "an"….

Answer 1

"Am Markt" can only be used figuratively, while "auf dem Markt" might be either direct or figurative. In other words, if you report prices, both "an" and "auf" are possible, but if you recount an anecdote of what happened to you last week-end on the Christmas fair, you need to use "auf". Other than that, I perceive very little difference.

Answer 2

"Am Markt" is frequently used in a business or economic context, it sounds more professional to me. It is however not related to "sich fortsetzen".

See also http://www.duden.de/rechtschreibung/auf_Praeposition

and

http://www.duden.de/rechtschreibung/am#Bedeutung1a