Portfolio performance graph for past 1Y (thru 3/13/2025):

GLD=37.82%

IAU=37.97%

IAUM=38.34%

using daily adjusted closing market price (from NASDAQ) integrating the logarithmic daily rate of return between 3/13/2025 to 3/14/2025 to calculate the cumulative rate of return, I calculate

GLD=31.34%

IAU=31.45%

IAUM=31.66%

These ETF's do not pay a dividend, Expense cost is included in the closing price.

The difference in rate of return is about 6%, which is too large. I can send you my calculation (xls) if this would be useful.

What is causing the error?

Hey, it's difficult to pinpoint the error without seeing your data and calculations.

I did a quick cross-validation using open data from Yahoo Finance, and here are the results for GLD:

• The latest close price is 275.24
• The close price on March 15, 2024, is 199.71
• The 1-year return is calculated as: (275.24/199.71−1)×100=37.82%
• We show 37.38% for the same period, which is pretty close. The small difference might be due to slightly different time ranges.

How did you get your numbers?