Download effect "statistically indistinguishable from zero"

There's a new paper out by some American academics on the effect
downloading has on music sales:

http://www.unc.edu/~cigar/papers/FileSharing_March2004.pdf

Abstract:

A longstanding economic question is the appropriate level of protection
for intellectual property. The Internet has drastically lowered the cost
of copying information goods and provides a natural crucible to assess
the implications of reduced protection. We consider the specific case of
file sharing and its effect on the legal sales of music. A dataset
containing 0.01% of the world.s downloads is matched to U.S. sales data
for a large number of albums. To establish causality, downloads are
instrumented using technical features related to file sharing, such as
network congestion or song length, as well as international school
holidays. Downloads have an effect on sales which is statistically
indistinguishable from zero, despite rather precise estimates. Moreover,
these estimates are of moderate economic significance and are inconsistent
with claims that file sharing is the primary reason for the recent decline
in music sales.  *We thank Shane Greenstein and participants at the 2004
AEA meeting for valuable comments and suggestions. We also acknowledge
Sarah Woolverton for her tireless efforts to improve the quality of our
song matching algorithm and Christina Hsiung Chen for research assistance. 
The CMJ Network, Nathaniel Leibowitz, and Nevil Brownlee generously
provided us with auxiliary data. Oberholzer-Gee gratefully acknowledges
the financial support of the George F. Baker Foundation. Aural support
from Massive Attack, Sigur Ros and The Mountain Goats is gratefully
acknowledged.