X-Message-Number: 32353 From: David Stodolsky <> Subject: Re: CI growth rate decreasing? Date: Tue, 2 Feb 2010 16:18:22 +0100 References: <> On 1 Feb 2010, at 11:00 AM, CryoNet wrote: > David's selection of data misrepresents the bigger > picture of what has been happening. Using data for > Cryonics Institute (CI) growth since 1990 gives: It is almost always possible to bias an outcome by selection of data. However, in my original analysis all data were included, unless there was a statistically valid reason for not doing so. The excluded data was from the first years and clearly had a different slope. Attempts to fit the remaining data compared simple curves, such as linear and exponential. Exponential growth of CI was the best explanation for the data. Next, it was noted that the slope of the exponential changed in 1998 and a test verified that change as statistically significant. Thus, using the data from 1998 forward gives us the best estimate of what growth should be in the Internet Age. These points are documented in the cited web page and in CryoNet messages around that time. So, the implication that data were selected to support a predetermined hypothesis is inappropriate. > > There was a growth > spurt in the 1997-2001 period which > is probably entirely attributable > to the fact that CI gained a website > and people started finding our > organization through the internet. My analysis showed that this 'spurt', that is, 23% yearly growth, continued thru 2004. I see no reason that the effect of the website would stop in 2001, unless there is a fixed pool of potential sign ups. If there is, then it supports the atheist millionaire hypothesis. However, drawing a conclusion after examination of the data is not considered to be a valid method of hypothesis testing. > Membership growth has been roughly > constant since 2001, with a spurt > in 2005, which I have attributed > to a New York Times article (we > had a huge spurt of growth in the > weeks of the time of that article. This is a fine hypothesis, but without systematic data collection making possible a correlation between publicity and growth, it can hardly be considered anything more than a post-hoc attempt to explain events. > > Selecting average growth from the > 1998-2004 period as a predictive base > is arbitrary, as compared to > 2001-2007 or 1990-1996. The selection was based upon a statistical test, which rejected the hypothesis that growth rates were the same before and after 1998. It was later noted that the website went online in that year and that this could explain the change. > Needless to say, these amounts of data > are not sufficient for statistically > significant prognostication The data is adequate to distinguish between alternative growth models of the simple type we are discussing here. The fit for the data for 1998 thru 2009 is significantly different at the .05 level, when linear and exponential models are compared. The linear model for members accounts for .99 Adjusted RSquared, while the exponential model accounts for only .96. CI total membership has been growing at 69 persons/year. Similarly, the fit for the suspendee data for 1998 thru 2009 is significantly different at the .05 level when linear and exponential models are compared. However, the linear model accounts for only .988 Adjusted RSquared, while the exponential accounts for .991. Thus, while the growth in suspendees remains exponential (when 2009 is included), it has dropped to 10%/year. (Here we can see the real problem of limited data, which is identification. When 1998 - 2008 data is fit, the linear model is better. However, when the 2009 datum is added, we get a slightly better fit with an exponential model. Either way, the data tells the same story, decreased growth compared to 1998 - 2004.) So, if we combine the results for both membership growth and suspendee growth, we can see decreases feeding thru the system. We would expect suspendee growth to lag membership growth, since in most cases people become members some time before they become suspendees. Therefore, the data is consistent with a decreasing growth rate at CI. The ALCOR data is problematic, since it has proceeded more in spurts (and even a decrease) and therefore can't be modeled with these simple curves, or probably at all, given the limitations of the data. However, I expect the same factors that influence CI growth to effect ALCOR growth. > Membership growth has > been roughly linear (constant number > of new Members each year) As I have mentioned earlier, this is a faulty metric, since it ignores the size of the organization. (Calculations must be on the raw data, that is, the total number of members, etc., if they are to be statistically meaningful.) If a big corporation stated it had a successful year, because it had attracted 3 new people, this would be seen as absurd. However, if the same statement was made by a startup which only had 3 customers to begin with, it could be seen as valid. So, let's agree to use the appropriate metric, which for organizational growth is the percentage increase per year. There is nothing new about these conclusions. There has been talk of 'stagnation' for some time and the recent 'teens and 20s' meeting was a recognition that there has been a drop in interest. I merely show what the situation looks like from a quantitative standpoint. My figures were conservative. Our best estimate of growth in the Internet age is 23%: Using the 1998-2004 rate of 23%/year): 163 suspendees predicted by 2010.1.1 85 suspendees actual by 2010.1.1 (Ten patients received from the American Cryonics Society in 2004 are not included. Thus 58 suspendees on 2005.1.1 and 85 suspendees on 2010.1.1) 1340 total members predicted by 2010.1.1 833 total members actual by 2010.1.1 (476 members on 20041.1) Growth in suspendees is only 52% of expected. Growth in members is only 62% of expected. We are certainly not heading toward the originally predicted five million CI members in 2044. The linear growth predicted above means only a few thousand CI members in 2044. If we review the entire history of CI growth, it is clear that the best fit is exponential. This is what we would expect to see, if each member attracted a new member with a fixed probability. The fact that people often recruit family members to sign up, is one example of this dynamic. So, the current trend toward linear growth represents a fundamental change in the outlook for cryonics. I have argued elsewhere that the movement may face a political crisis in which political power will be the deciding factor and therefore numbers will be crucial. If this is correct, then the future of all cryonicists is at risk, if this new growth pattern persists. dss David Stodolsky Skype: davidstodolsky Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=32353