Why Historical Volume Can Differ Across Market Data Providers

Summary

The document raises a practical data-quality question: why Interactive Brokers historical stock volume can be much lower than figures from other providers. It describes a comparison across several US equities and dates, reporting discrepancies that vary by symbol and day, with the largest examples reaching roughly half or more of the other displayed totals. The questioner has already considered regular trading hours, lot-size conversion, and exchange routing, and cites the broker’s disclosure that its historical feed filters certain trade types, including some off-NBBO activity.

The document asks whether filtered trades, including activity associated with dark pools, could account for the gaps, but supplies no answer or verified explanation. Its useful lesson is that daily volume is feed-dependent and that matching ticker and date alone does not ensure comparable totals. The table is anecdotal rather than a systematic audit: it does not establish the sources’ coverage definitions, trade-condition filters, corrections, or aggregation methods. Researchers should confirm these details with each provider before treating the figures as interchangeable or using them in volume-based analysis.

Key ideas

• Historical volume totals can differ materially across market data providers.
• Interactive Brokers is described as filtering some trades that occur away from the NBBO.
• The examples show that the size of the reported discrepancy varies across securities and dates.
• The document poses possible causes but does not establish whether dark-pool activity explains the differences.
• Provider definitions and trade filters should be checked before comparing volume series.

Tags

# How can you explain the substantially lower trading volume shown in IBKR?


# How can you explain the substantially lower trading volume shown in IBKR?












I am using IBKR API to download historical data. The trading volumes are always substantially lower than from Yahoo Finance and Nasdaq.com, often lower by 50%. It is impossible to be explained by regular trading hours. I see some other posts saying regular lot of 100 shares etc so should multiply by 100; I think that is already corrected and is irrelevant here. I am setting SMART as the exchange already and my data match those from running the sample codes so my codes are correct.

I do see on its doc that,

> IB's historical data feed is filtered for some types of trades which generally occur away from the NBBO such as combos, block trades, and derivatives. For that reason the historical data volume will be lower than an unfiltered historical data feed.

But the difference is way too large. How is it possible for volumes to differ so massively? Does it have anything to do with darkpools etc?

For example:

| Ticker | Date | Nasdaq/Yahoo | IBKR | %diff |
| AAPL | 20240628 | 82,542,720 | 42,812,041 | 50% |
| AAPL | 20240627 | 49,772,710 | 31,916,744 | 30% |
| AMD | 20240628 | 56,204,620 | 41,151,992 | 30% |
| AMD | 20240627 | 34,018,220 | 26,066,024 | 20% |
| TSLA | 20240624 | 61,992,070 | 47,662,995 | 20% |
| META | 20240626 | 8,882,337 | 4,309,977 | 50% |
| APP | 20240625 | 4,042,492 | 2,085,910 | 50% |
| BOX | 20240627 | 1,621,128 | 694,668 | 60% |
| BASE | 20240628 | 2,320,411 | 612,166 | 70% |
| CAT | 20240628 | 8,891,479 | 1,704,328 | 50% |
| OXY | 20240624 | 10,315,120 | 6,688,195 | 30% |
| KO | 20240627 | 8,494,123 | 4,918,846 | 40% |

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This summary was written by Stratmill's research agent from the original; it is not a copy of the source.