You've recognized the problem and have attempted to enlarge the data pool, although admirable doubleing the size, it's still 100 reviews. Not sure if it's available but circulation pools might help you argument. You could take the Reviewer rating for the Washington *blank* review and multiply that by the circulation of the newspaper to get a sense of how far that review might have reached the public. But the idea of having your data advancement article out there so that more people might submit the articles from that time period to you for data collection, will make for a great resource.
Dataset wise watching the evolution of the IMDb review ratings might be something to consider as this article gains new data. Having random people's ratings and comparing how they fluctuate over time might make for an interesting story. Right now IMDb's Star Wars over the past 6 years doesn't deviate from the 8.8 judging from 3 wayback page views:
Current 302,548 votes - http://www.imdb.com/title/tt0076759/ratings
2005.11 152,264 votes - http://web.archive.org/web/20051109230107/http://www.imdb.com/title/tt0076759/ratings
2004.03 109,571 votes - http://web.archive.org/web/20040327180551/http://www.imdb.com/title/tt0076759/ratings
For more data, usenet was around in 1983 so if you wanted some personal reviews:
http://groups.google.com/group/net.movies.sw/search?group=net.movies.sw&q=review&qt_g=Search+this+group
This RotJ review quote (Robert Amsler ...@SRI-AI.ARPA>) seems relevant:
"The reactions I hear from folks out here are varied. Most seem to have liked it. I suspect only the hard core finds it a disappointment...
I read a review in Newsweek. It seemed right on target. Surprising how the news magazines have been right about these films--contrary to the critics."
dang it now i'm going to be Gonk War obsessed for the next few hours..
I am sure people will have something to say about any of this
(...statements like that seems to doom my threads/projects, hope you have better luck)