The trendline is an imaginary observation of the past based on guesstimations of a lagging slope and an arbitrary formula for an exponential growth of the userbase in which the exponent could easily be wrong causing a massive error.
thats shark jumping. the exponent error point is the good point in your post. i should like to take fits over time to observe the variance. stupid tax deadline has me stretched tho.
I don't know where I saw a couple of days ago the graph with the curve representing where the exponential would be taking in count only data up to that time. It has been remarkably close to current trendline for over a year. I think rpietila already said this when introducing his model and since then has talked of how little the slope changes month-to month but has not repeated it enough, apparently, given that it is a very strong point to which oda.krell raised an objection too.
Starting at 2009-01-03,
X-axis resolution daily.
Y-axis log(USD/BTC) (red line);
log(price)/log(trend_price) (blue line) <-
trendline recalculated monthly; this graph uses 36 individual trendlines 2011 I bought at this point of the trendline (-0.35).
12/2013 decided that it will possibly go to about -0.35 but to be on the safe side I calculated 410 to be the buy zone in 2-3/2014 (-0.3 in 2014-3-31).
Now it strongly points out that we are oversold, since never before in Bitcoin's history has the price gone down from a condition this much below the trend. The price/trendline-differential has gone deeper but it has been accompanied with a rising price (11/2011-12/2012).
To underline the novel method used here:
the trendline (not shown, only the price (red) and the difference of price and trendline (blue) are shown)
is recalculated every month so that its parameters constantly change.
As far as I know, there is much critique against the trendline but none of it stems from understanding. The valid attack vectors are:
- Is the dataset reliable in describing the phenomenon? (yes; the very beginning is uncertain because there were not many trades, but leaving it out, leads to greater arbitrariness than using as representative the data as we can generate)
- Can it reasonably be modelled using the given trendline model? (yes; this is about technology adoption, which can follow logistic function)
- Is the trendline best fit to the data? (yes, its R^2 is the highest)