Sales of recorded music sales fell by more than 7% around the world in 2003, the International Federation of Phonographic Industries (IFPI) reports.
The IFPI says music sales have fallen 19% in Germany alone
But the average figure included much bigger declines in some countries, such as a 19% drop in Germany, it said.
It added there were "double-digit" drops in sales in other countries, including Denmark and Switzerland.
The IFPI said internet piracy was a major factor in the decline. It said sales had fallen 20% over three years.
Other countries suffering a 10% drop or more include France, Sweden, Belgium, Greece, Ireland and Portugal.
The global music market is now worth more than $32bn (£17.7bn), according to the IFPI figures.
"Research by IFPI and numerous independent third parties overwhelmingly proves that unauthorised file-sharing translates directly into lost legitimate music retail sales," the federation said.
But there the IFPI said there were also positive signs, with the drop in music sales easing off in the US thanks to "robust" album sales and the boom in music DVDs.
Music DVDs now count for nearly 6% of music sales in the US, the IFPI said.
Legal downloads in the US rose to 19.2 million last year, partly due to the launch of Apple's iTunes service.
However, another study has suggested internet downloads and trading on "peer-to-peer" are not responsible for the decrease in sales.
Their effect is "statistically indistinguishable from zero," authors Felix Oberholtzer of the Harvard Business School and Koleman Strumpf of the University of North Carolina-Chapel Hill wrote.