If the aggregating hit rate for all of the Ganzfeld is considered in isolation, the existence of psi in the ganzfeld has been proven beyond any doubt. Consider a skeptic's 'conservative estimate' of the total hit rate (of which he personally tallied) of all post-1970 Ganzfeld: 28.6% over 6700 trials(SkepticReport.com). P(chance) = (1 - 0.999999999988614).
Unfortunately, the claims of methodological flaws as a cause of the abberations from chance still dominate some critic's minds, even if these these claims are absolutely baseless. What all camps acknowledge, including the fundamentalist skeptics, is that the methodological rigour of psi-setups has improved to the point where accusations of methodologic flaw hold no basis in reality. However, as for the Ganzfeld, researchers have not yet delivered the final nail into the denier's coffins. What, if possible, should be shown is that there exists either neutral (or positive, although there'd be no reason for this) correlation between continually increasing methodological rigour/reporting requirements and ES. Of course, some parapsychologists maintain that this is difficult due to a number of possible constraints. Unfortunately though, this has never been attempted for the entire database of the Ganzfeld. If and when this is done for the Ganzfeld, the Ganzfeld setup will have been epistemically, beyond all doubt, proven to be demonstrating Psi effects.
The reason I am commenting on this is because there exists an attempt at plotting an ES regression for the Ganzfeld database; yet, the database isn't a database, it's missing half of the data!
http://tinypic.com/view.php?pic=dq409u&s=5 (Bierman 2000)
There are numerous reasons why this graph doesn't do justice to the Ganzfeld data. Firstly, the pre-1986 data has been directly taken from Honorton's meta analysis (1985) of 28 Direct-Hit studies. These were markedly more successful (37% hit rate) than the Non-Direct-Hit studies, of which there were 14 studies. Whilst Honorton had perfectly sound reasons for excluding it from his meta-analysis, it causes an artifactual ES skew between 1970-1986.
Moreover, this ES regression assumes that Honorton's meta-analysis was overarching of the pre-autoganzfeld database, which it certainly was not. Storm & Ertel (2001) defined 11 Direct-Hit studies in between 1982-1986 that were excluded from Honorton's analysis; they called this database the 'S&E' database. 'The S&E database had an unweighted ES of 0.222 (SD = 0.23) and a Stouffer Z of 3.46 (p = 2.70 x 10E-4)' (Storm & Ertel 2001). Of course, this would have a significant effect on the supposed ES decline. I propose that if all Non-Direct-Hit data and this S&E data are accounted for in an appropriate way this data set may achieve an incline in ES leading to the end of the Old-Ganzfeld series, positively correlated to an inevitable increasing of methodological rigour.
Another concern with this regression is that it, whilst not in any fault of its author(s), discludes the successful post-MiltonWiseman experiments. These 10+ (highly significant) experiments will likely push the ES into pre-Hyman levels, essentially debunking the notion that methodological flaws are causing the success of the Ganzfeld.
It also seems that this regression was operating under the assumption that the Milton-Wiseman meta-analysis' exclusion criteria was sound. If not, you would have to wonder what exclusion/inclusion criteria Bierman used. Since it was not stated, I'd say it's safe to assume he stuck to Milton-Wiseman's critera and just included the experiments in that meta-analysis. This is a concern as this criteria was heavily criticised within the parapsychological community.
The graph should look more like this:
As can be seen, the inclusion of the S&E and post-M&W databases would change the entire nature of the Ganzfeld ES regression. Further, I believe we must account for the non-direct-hit studies in the pre-joint-communique database in a statistically appropriate way, not only for statistical integrity, but to fully eliminate the charge of a diminishing ES. Also, I strongly believe that the above graph should be treated for the uniquely atypical musical target studies.