| # Bitcoin complex-network study — data-processing notes |
| Derived from: Aspembitova, Feng, Melnikov & Chew (2019), *Fitness preferential attachment as a |
| driving mechanism in bitcoin transaction network*, PLoS ONE 14(8): e0219346. |
| Target: extend their framework from 2013 to the 2013–2026 era. |
|
|
| ## 1. What the paper did (must be replicated for comparability) |
| - Node = **user** = cluster of addresses (Reid–Harrigan heuristic: all input addresses of a |
| multi-input tx belong to one entity). Source: Brugere's dataset, ref [46]. |
| - Edge = one transaction (directed, weighted by BTC amount), **multi-edges retained**. |
| - Periods: 1P = 2009–2010, 2P = 2011–2012. Scale: 11.4M links, 4.7M nodes (2P). |
| - Windowing: monthly for assortativity / avg degree / clustering (daily "too sparse"); |
| daily used only for size-vs-price. |
| - Metrics: in/out/total degree + CCDF, power-law exponent (powerlaw pkg; Clauset–Shalizi–Newman |
| MLE+KS), global clustering, avg degree, assortativity, active/inactive/dead/resurrected |
| states, longevity (active months before death), fitness |
| `x_{i,n} = Δk_{i,n} / Σ_j Δk_{j,n}` (share of new links gained in month n). |
| - Findings: NO degree PA, NO wealth PA; fitness is power-law (α≈2) and ~constant in time; |
| corr(fitness, degree)=0.47; corr(age, degree/fitness)≈0.02–0.03; links grow ~linearly with |
| nodes (no accelerated growth); generative model (fitness PA + birth/death, 2/3 of new nodes |
| attach to new nodes) reproduces degree distribution but NOT clustering (0.12 vs 0.24). |
| - Gap: dataset ends 08 Jan 2013. The whole mature era is untouched. |
|
|
| ## 2. Measured properties of the modern data (AWS Open Data, day = 2026-09-01) |
| Schema per tx: txid, block_hash, block_number, block_timestamp, date, index, size, vsize, |
| lock_time, input_count, output_count, is_coinbase, fee, input_value, output_value, |
| inputs[] = {address, index, value, type, script_hex/asm, sequence, spent_transaction_hash, |
| spent_output_index, txinwitness[], required_signatures}, |
| outputs[] = {address, index, value, type, script_hex/asm, required_signatures} |
| |
| Day 2026-09-01: 627,345 tx | 1,140,645 inputs | 1,462,070 outputs | 142 coinbase | |
| 72,106 multi-input tx (11.5%) | mean in 1.82, mean out 2.33 | 1,010,472 BTC gross out-value. |
| |
| | issue | measurement | consequence | |
| |---|---|---| |
| | input address resolution | 704 / 1,140,645 missing = **99.94% resolved** | clustering heuristic has material | |
| | output address resolution | 360,057 / 1,462,070 = **24.6% have NO address** | OP_RETURN/data-carrier (ordinals) outputs vanish silently in an address-level graph; ~0% in 2013 | |
| | change / address reuse | 449,046 / 627,345 = **71.6% of txs share an address on both sides** | after user-clustering most edges become self-loops — must be an explicit policy, report both | |
| | multi-input (merging power) | 11.5% of txs | only these merge clusters; worth trending over time | |
| | coinbase | 142/day | flag & exclude or miners are permanent hubs | |
|
|
| ## 3. Data-processing decisions to lock before running |
| 1. **Entity level**: address-level (clean baseline, no heuristic) vs user-level (paper-comparable) |
| vs UTXO-level. Recommend building address-level first, then user-level via clustering. |
| 2. **Clustering guards** (2013 heuristic breaks in 2026): exchange batching and consolidation |
| create legitimately multi-owner multi-input txs → false mega-clusters; CoinJoin (equal-valued |
| outputs) merges strangers. Need: cluster-size cap, CoinJoin detection, exchange-address lists, |
| and a sensitivity analysis over the merge rule. |
| 3. **Self-loop policy**: keep vs drop (affects degree tails); report both. |
| 4. **No-address outputs**: drop, bucket as anonymous, or count as data-carrier activity. |
| 5. **Coinbase**: exclude from the transaction network; keep for issuance/subsidy series. |
| 6. **Weights**: BTC amounts are non-stationary in value → use supply-share or USD for wealth |
| attachment; keep raw BTC for volume. |
| 7. **Windowing**: monthly for structure; daily only for bursts/event studies. Within-block order |
| is miner-determined, not chronological — block_timestamp is the finest honest ordering. |
| 8. **Fitness**: needs per-window Δk per node + total Δk; zero-activity nodes excluded; requires |
| explicit birth/death/resurrection bookkeeping. |
| 9. **Periods**: do not inherit 1P/2P. Run data-driven change-point detection (regimes ~2009-10, |
| 2011-13, 2014-16, 2017, 2018-20, 2021-22, 2023+ ordinals). |
| 10. **Power-law rigor**: MLE + KS + likelihood ratio vs lognormal (powerlaw pkg / CSN); never OLS |
| on log-log. |
| 11. **Scale**: 1.45B tx / ~2B addresses. Full-graph clustering, path lengths and triangles are |
| infeasible naively → monthly windowed graphs, streaming/approximate algorithms, |
| DuckDB + networkit/graph-tool/igraph. The paper's full graph was 11M edges (≈130× smaller). |
| 12. **Reproducibility**: paper's dataset is STILL LIVE at |
| https://dynamics.cs.washington.edu/nobackup/bitcoin/bitcoin.tar.gz (679 MB, 2018-01-19) → |
| reproduce first, then extend on AWS parquet (s3://aws-public-blockchain/v1.0/btc/, |
| 2.19 TB total, 146 GB for 2026 YTD). |
| |
| ## 4. Storage/compute plan |
| - Paper reproduction: 679 MB (fits anywhere, no GPU). |
| - 2024→now slice: 561 GB (fits in the 972 GB free). |
| - Full 2.19 TB history: needs external 4 TB drive or query-in-place over HTTP (DuckDB httpfs, |
| verified working: footer/schema + projection pushdown without full download). |
| |
