How can one realistically model the distribution of the network's unspent transaction outputs?

I haven't read any papers trying to analyze the amount of unspent outputs. More often, people are interested in the distribution of address' balances. This could be interesting because it reflects how evenly distributed bitcoin is.

I did find this article: http://www.coindesk.com/what-block-chain-analysis-tells-bitcoin/, which seems like it might be of interest to you and is related to the distribution of UTXOs.

If you call gettxoutsetinfo with the Bitcoin Core RPC calls, it tells some basic info about the UTXO set. I just did this and got:

{
    "height" : 338396,
    "bestblock" : "000000000000000009f32437cb28d54ff600ec020778c8ce84ecf93b99d5218c",
    "transactions" : 4525842,
    "txouts" : 16217914,
    "bytes_serialized" : 566046691,
    "hash_serialized" : "1ad2172e4d37ce21291c116580f5b527e4c302b9c2ce4e88a91c0c00f748fb8d",
    "total_amount" : 13709764.78496462
}

So it seems that the average amount of an UTXO is:

13709764.78496462 / 16217914 = 0.84534699

To analyze the amount of outputs (note, this is not only UTXOs), I wrote up this quick script:

<?php

require_once 'jsonRPCClient.php';

$bitcoin = new jsonRPCClient('http://{username}:{password}@127.0.0.1:8332/');

$info = $bitcoin->getinfo();

$height = $info['blocks'];
$numTrials = 1000;
$includeCoinbase = false;


$cutoffs = array();

for ($i = 0; $i < 10; $i++) { $cutoffs[] = $i; }
for ($i = 1; $i < 10; $i++) { $cutoffs[] = 10*$i; }
for ($i = 1; $i < 10; $i++) { $cutoffs[] = 100*$i; }
for ($i = 1; $i < 10; $i++) { $cutoffs[] = 1000*$i; }

function GetRange($value) 
{
    global $cutoffs;
    for ($i = 0; $i < count($cutoffs)-1; $i++)
    {
        if ($cutoffs[$i] <= $value && $value < $cutoffs[$i+1])
            return $cutoffs[$i] . " - " . $cutoffs[$i+1];
    }
    return $cutoffs[count($cutoffs)-1] . " - ...";
}

$sum = 0;
$distribution = array();

for ($i = 0; $i < $numTrials; $i++) 
{

    $blockhash = $bitcoin->getblockhash(rand(1, $height));
    $block = $bitcoin->getblock($blockhash);

    $randTxIndex = rand(0, count($block['tx'])-1);

    if ($randTxIndex == 0 && !$includeCoinbase) {
        $i--;
        continue;
    }

    $randTxHash = $block['tx'][$randTxIndex];

    $randTx = $bitcoin->getrawtransaction($randTxHash, 1);

    $numOutputs = count($randTx['vout']);
    $randOutput = $randTx['vout'][rand(0, $numOutputs-1)];

    $value = $randOutput['value'];

    $sum += $value;
    $distribution[GetRange($value)] += 1;
}

echo (json_encode($distribution, JSON_PRETTY_PRINT) . "\n");
echo "average: " . ($sum / $numTrials) . "\n";

And the results are (after being cleaned up a little):

average: 89.55518291596

START   END     COUNT
0       1       636
1       2       73
2       3       18
3       4       20
4       5       14
5       6       11
6       7       8
7       8       8
8       9       11
9       10      12
10      20      36
20      30      26
30      40      15
40      50      16
50      60      29
60      70      5
70      80      5
80      90      4
90      100     3
100     200     29
200     300     4
300     400     4
400     500     1
500     600     1
600     700     1
700     800     1
800     900     3
900     1000    0
1000    2000    2
2000    3000    1
3000    4000    0
4000    5000    0
5000    6000    1
6000    7000    0
7000    8000    0
8000    9000    0
9000    ...     2

Which, when plotted, gives:

enter image description here

And since the 0-1 outputs make the rest go out of scale, this is a plot without the smallest outputs:

enter image description here

morsecoder

Posted 2014-10-03T09:44:40.563

Reputation: 12 624

The Start and End figures, is that satoshis or bitcoins? Thank you for your hard work! – Murch – 2015-11-05T23:14:37.170

1All of those questions would be answerable from the block chain. I would plot it as a histogram with x being the value of the UTXOs and y being the number of them. – Tyler – 2014-10-03T12:55:45.217

There's multiple properties related to UTXO that come to my mind (e.g. index number, amount, script, txid, age...) - distribution of what quantity do you mean? Try to be more specific please. – Jozef – 2014-10-19T12:41:08.420

@JozefKnaperek: Thanks, I was too much in the topic to realize that you could read it in so many different ways. I hope it is clearer now. – Murch – 2014-10-19T13:06:53.727

@Tyler: Yeah, I am aware of that. However, my question was, whether I have to do that work, or if someone else already has. – Murch – 2014-10-19T13:07:34.070

OK, makes sense to me now. But I haven't seen such analysis so far; I've found some nice online charts, but none of them does seem to be exactly what you're looking for. You can contact them though and they might add it (i.e. do the work for you :-)). Otherwise I guess you're on your own.

– Jozef – 2014-10-19T14:09:15.977

UTXO's are stored in the Chainstate. Something like Levelhud to make navigating it better.

– KJ O – 2014-10-19T22:44:31.013

How can one realistically model the distribution of the network's unspent transaction outputs?

Answers