Bitcoin Forum

You've seen the...

Graph of Total Bitcoins Over Time

I'm curious. Isn't that just sort of an ESTIMATE based on TODAY'S CPU speeds?

The graph is here:
http://www.bitcoin.org/wiki/lib/exe/detail.php?id=bitcoins&media=total_bitcoins_over_time_graph.png

I'll leave it to someone else to explain how it isn't an estimate based on CPU speed.

The bitcoins earned per block ("subsidy") will halve at 210,000 blocks, regardless of the network's CPU speed. The problem is in determining how fast we'll get to that point.

The generation difficulty adjustment tries to keep the rate of blocks per hour constant, so the chart won't be far off. The timing of the chart might be a little late because the CPU speed of the network is constantly growing, so blocks are currently being produced more frequently than they should be. Once growth stops in a few years, it'll be possible to predict the times of future subsidy adjustments more accurately.

So the chart is not affected per se by total CPU speed, but by growth/reduction in that speed.

There are currently 4.56 million bitcoins. Looking at the graph, it seems to be very close to the current reality.

My old prediction (http://bitcointalk.org/index.php?topic=93.msg836#msg836) said there'd by 4.02 million now, so we are a bit ahead.

We can get ahead for now, but we can never get above 21 million. This is because every 210000 blocks the reward halves 50, 25, 12.5... until it is gone and tx fees are the sole motivation for generating. The date at which this happens can change but there will never be 21 million coins. It's a few coins under because the halving rounds down to the hundred millionth.

It is not particularly likely to happen early either because of difficulty adjustments. We are in a long term growth period now and the diff adjustment never gets us down below 6/hr for any length of time. I'd guess the first time this happens for very long will be the first summer (northern hemisphere) after near complete bitcoin acceptance, but that's a total guess.

Can we get a new graph made that predicts future generation based on past average block intervals, as opposed to the target intervals?  I understand that past performance doesn't lead to future performance, but for a while yet it might prove to be a better indicator of the pace of bitcoin generation.

So doesn't that mean that reaching 21,000,000 is likely to happen early, because the blocks per hour is averaging 9 or whatever?

The rate of generation is somewhat arbitrary anyway, and whether 21 million is reached a decade or a century after I'm dead doesn't make much difference to me.

Within a couple of decades we'll be past 20 million. After that time my guess is that the rate of coin loss will be a bigger factor than the rate of coin generation.

Just speculating here.

When difficult "overshoots" we will pay back a bit more time than the comparable sized "undershoots" that we've been doing have gotten us ahead.

If we do 9/hr (50% over) for 2016, then 4/hr (50% under) for 2016 this takes 224 + 504 = 728 hours which is longer than 336 + 336 = 672 hours.

So essentially were just in an extended period where we haven't paid any time back and it might not come for a long time.

I'm not really sure, and I don't have a solid conclusion here. I think smooth growth in power gets us ahead, but jerks up and down get us behind. Maybe someone can write a simulation (or just do better math than me).

Average blocks per 24 hours for the last x blocks:

Last 100: 177.8
Last 200:175.3
Last 400: 201.4
Last 800: 207.2
Last 1600: 222.1
Last 3200: 212.3
Last 6400: 215.5
Last 12800: 194.2
Last 25600: 207.7
Last 51200: 188.6
All time: 134.8

Some graphs using those numbers (x axis is always "days from now"):
Last 400 blocks - 201 blocks per day
http://img602.imageshack.us/img602/1323/400.png
Subsidy adjustment: June 25, 2012

3200 - 212 blocks per day
http://img84.imageshack.us/img84/2149/3200z.png
Subsidy adjustment: May 26, 2012

12800 - 194 blocks per day
http://img139.imageshack.us/img139/7711/12800.png
Subsidy adjustment: July 17, 2012

All time - 135 blocks per day
http://img691.imageshack.us/img691/3380/alltime.png
Subsidy adjustment: April 10, 2013

The difficulty algorithm is not that smart.  It doesn't attempt to make up for previous underguessed weeks beyond the past two.  No fuzzy logic code.

Thanks, but I was hoping it would be more consistent than that.  No trendline apparent there.

I know. I didn't mean to imply that it was doing anything complicated. Maybe I should have phrased it all from the side of the mass of people generating since that's the fickle side. It has been, more and more generating for a long time now, when/if that reverses we will slow down.

Maybe I'm stating the obvious in a stupid way, I don't know.