For those who actually use VL data this is my method for checking the quality of the data. I compare the prices in the VL file with an accurate database I store daily. I do this for AAPL and IBM. When they are a match I consider the file to be OK, and when not, GARBAGE. I do not consider the Total Return values, but only the CLOSE price for each weekend file. This is what the conclusion is for 2025.

File        Close       
Date        Date        Verdict
12/27/2024              
1/3/2025    12/27/2024  OK
1/10/2025   1/3/2025    OK
1/17/2025   1/10/2025   OK
1/24/2025   1/17/2025   OK
1/31/2025   1/24/2025   OK
2/7/2025    1/31/2025   OK
2/14/2025   2/7/2025    OK
2/21/2025   2/14/2025   OK
2/28/2025   2/21/2025   OK
3/7/2025    2/28/2025   OK
3/14/2025   3/7/2025    OK
3/21/2025   3/14/2025   OK
3/28/2025   3/21/2025   OK
4/4/2025    3/28/2025   OK
4/11/2025   4/4/2025    OK
4/18/2025   4/11/2025   OK
4/25/2025   4/17/2025   OK
5/2/2025    4/25/2025   OK
5/9/2025    NONE        GARBAGE
5/16/2025   4/25/2018   GARBAGE
5/23/2025   4/25/2018   GARBAGE
5/30/2025   5/23/2025   OK
6/6/2025    4/25/2018   GARBAGE
6/13/2025   6/6/2025    OK
6/20/2025   6/13/2025   OK
6/27/2025   6/20/2025   OK
7/4/2025    4/25/2018   GARBAGE

When it says NONE that means there are no prices for the full history of IBM and AAPL that are a match to the prices they've stored in their file. You'll note that when it is GARBAGE the date of the CLOSE prices are consistently 4/25/2018. This means that when they fail they tend to just keep using that same file again and again.

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