Newspaper takes a LOT longer than that to decompose if it is in a landfill. There was a report back in the 80's about recovering newspapers from the 1950's in our local landfills.
How fast something decomposes is not that cut and dry.... I put banana peels, apple cores, Orange peels even some prunings if they are about thumb size or smaller in a compost pile (turned most every day) it all goes away in about 2-6 weeks (ok, the prunings might take a few months)
The material, how tight it is packed, how much it is airiated, how acidic the base is. all has an impact on the time.
In landfills, the necessary microbes, air and/or moisture might not be available to get the decomposition process moving along so some biodegradable items might hang around longer than they should. http://environment.about.com/od/recycling/a/biodegradable.htm
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The material, how tight it is packed, how much it is airiated, how acidic the base is. all has an impact on the time.