Data quality issue: corrupted NAV data of mutual funds

Hi there!

We downloaded data for more than thousands mutual funds and ETFs to build a proprietary fund database. After some descriptive analysis, we found out that about 50% of funds have extreme returns that aren’t correct (verified and cross-checked manually with external data sources). In other words, the NAV and return data seems to be corrupted. We dug deeper into this and tried out different functions and methods to download the data (see the PDF for the code). There we intentionally tried funds whose data is corrupted. All tested methods return historical NAV data with extreme returns (>50%, >100%). These jumps do not reflect actual fund performance and appear to be caused by:

• Fund splits/consolidations not being adjusted

• Data source inconsistencies

• Missing adjustment factors

The issue persists across different API methods and fields. Interestingly, we manually downloaded the data for these funds using the Excel Add-In and got the correct data without any extreme returns, suggesting different data sources.

However, we cannot download the NAV and return data for thousands of funds via the Excel Add-In. The corrupted data from the Codebook renders our project useless. Any ideas what we could do?

Thanks a lot in advance!

Marvin

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Jirapongse

@TertiumFamilyOffice

Thank you for reaching out to us.

Typically, the data retrieved using the =RDP.Data function in Workspace Excel should match the output from the rd.get_data method, provided that the same RICs, fields, and parameters are used.

Could you please share a sample output from a basic rd.get_data method call, along with the corresponding output from the =RDP.Data function in Excel? This will allow us to compare the results effectively.

For example:

Jirapongse

I tested the code.

The first method returns this message.

METHOD 1: ISIN + TR.FundNAV
✓ Retrieved 2928 data points
✓ Date range: 2013-10-14 to 2025-01-01
✓ Max absolute return: 98.99%
Returns >50.0%: 1
PROBLEMATIC DATES (showing first 5):
2021-10-07: -98.99% (NAV: 0.8069)

The data in the data frame is:

	Instrument	NAV	Date	Daily_Return
2083	IE00BD3QHZ91	0.806913	2021-10-07	-0.989911

This is the data from Excel.

The second method returns the following message.

METHOD 2: Lipper ID + TR.NETASSETVAL
✓ Retrieved 2928 data points
✓ Date range: 2013-10-14 to 2024-12-31
✓ Max absolute return: 98.99%
Returns >50.0%: 1
PROBLEMATIC DATES (showing first 5):
2021-10-07: -98.99% (NAV: 0.8069)

The data in the data frame is:

	Instrument	NAV	Date	Daily_Return
3069	68280971	0.806913	2021-10-07	-0.989911

This is the data from Excel.

For the third method, I checked with the Data Item Brower tool and found that the TR.FundNav field doesn't support the Adjusted parameter.

Therefore, this could be a content issue. You can contact the content support team directly via LSEG Support to verify the content.

TertiumFamilyOffice

@Jirapongse

Thank you for your messages and help.

Yes, I will address this issue with the content team. Apparently, thousands of funds are affected by this issue, which is a serious problem.

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