How to calculate the account return rate

There are multiple methods to calculate the return on a securities account, such as the simple return method and the compound return method. Considering that account funds are subject to inflows and outflows, how can the return during this period be objectively reflected and avoid distortion? I use the net asset value (NAV) method, treating the account as a fund, with fund inflows and outflows regarded as subscriptions and redemptions.
Between 2019 and 2025, my account experienced 16 transactions (some data hidden due to size constraints). By calculating the monthly return using the NAV method, I can plot the account’s monthly net value changes alongside the Shanghai Composite Index trend (setting the initial capital and the Shanghai Index at the end of 2018 to 1). Over seven years, the account’s net value increased from 1 to 2.173, with an average annual return of 16.76%. The Shanghai Index grew from 1 to 1.591, with an average annual growth rate of 8.44%.