There was a heavy police presence in the city for the Anti-Internment League parade, which marked the anniversary of the introduction of detention without trial in Northern Ireland in 1971.The republican parade, and loyalist protest, passed off with only minor disturbances. Last year, serious rioting erupted during the rally which left dozens of PSNI officers injured.Although the weekend's parade passed in minutes, and the area then fully reopened for business, the usual crowds of Sunday afternoon shoppers avoided the city centre.Some traders believe the potential for trouble and the huge security operation simply put people off coming into the city - they simply want the opportunity to do business without disruption.Paul McMahon, Belfast City Centre Management, said: "It was a very poor day for trade. We have retailers telling us they were down as much as 70% on the same day last year and clearly that's not very good and that's something that needs to addressed."We need our political leaders to resolve that because it is something that we can't continue with."The Mourne Seafood Bar, a popular city centre restaurant, estimate that Sunday's disruption cost the business thousands of pounds.Owner Andy Rea said: "Pretty much our sales were down by half. I mean, when the parade is on or any sort of parade or protest is on and you have that police presence in town, you might as well wipe out that part of the day."Generally afterwards, we do get people coming back into town but you know yourself you walk into town you see loads of landrovers, lots of police or security presence it sort of puts you off coming out."Glyn Roberts, of Northern Ireland Independent Retail Trade Association ( NIIRTA), said that it "wasn't a particularly good day for Belfast.""Also there were lots of tourists, there was a cruise ship in. So we've got to be conscious of what impact these parades and protests have on the city both national and internationally."