Created
January 31, 2019 10:31
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Calculate Gini coefficient for Bitcoin balances.
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WITH double_entry_book AS ( | |
-- debits | |
SELECT | |
array_to_string(inputs.addresses, ",") as address | |
, inputs.type | |
, -inputs.value as value | |
, block_timestamp | |
FROM `bigquery-public-data.crypto_bitcoin.inputs` as inputs | |
UNION ALL | |
-- credits | |
SELECT | |
array_to_string(outputs.addresses, ",") as address | |
, outputs.type | |
, outputs.value as value | |
, block_timestamp | |
FROM `bigquery-public-data.crypto_bitcoin.outputs` as outputs | |
) | |
,double_entry_book_by_date as ( | |
select | |
date(block_timestamp) as date, | |
address, | |
sum(value / POWER(10,0)) as value | |
from double_entry_book | |
group by address, date | |
) | |
,daily_balances_with_gaps as ( | |
select | |
address, | |
date, | |
sum(value) over (partition by address order by date) as balance, | |
lead(date, 1, current_date()) over (partition by address order by date) as next_date | |
from double_entry_book_by_date | |
) | |
,calendar as ( | |
select date from unnest(generate_date_array('2009-01-12', current_date())) as date | |
) | |
,daily_balances as ( | |
select address, calendar.date, balance | |
from daily_balances_with_gaps | |
join calendar on daily_balances_with_gaps.date <= calendar.date and calendar.date < daily_balances_with_gaps.next_date | |
) | |
,supply as ( | |
select | |
date, | |
sum(balance) as daily_supply | |
from daily_balances | |
group by date | |
) | |
,ranked_daily_balances as ( | |
select | |
daily_balances.date, | |
balance, | |
row_number() over (partition by daily_balances.date order by balance desc) as rank | |
from daily_balances | |
join supply on daily_balances.date = supply.date | |
where safe_divide(balance, daily_supply) >= 0.0001 | |
ORDER BY safe_divide(balance, daily_supply) DESC | |
) | |
select | |
date, | |
-- (1 − 2B) https://en.wikipedia.org/wiki/Gini_coefficient | |
1 - 2 * sum((balance * (rank - 1) + balance / 2)) / count(*) / sum(balance) as gini | |
from ranked_daily_balances | |
group by date | |
order by date asc |
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