I now have a bee in my bonnet about this, and did some googling. Apologies for the lengthy post.
To try and compare apples to apples, I went to the Vanguard Pages for VFIFX (Vanguard Target Retirement Fund 2050), VTSAX (Vanguard Total Market Index Admiral), and VTI (Vanguard Total Market ETF). I also looked up their pages on MarketWatch, Fidelity, and Morningstar.
Vanguard pages are at:
https://investor.vanguard.com/mutual-funds/profile/overview/vtsaxhttps://investor.vanguard.com/mutual-funds/profile/overview/vfifxhttps://investor.vanguard.com/etf/profile/overview/vti As mentioned earlier in this thread, there's no direct equivalent to the Target Date Funds in ETFs, so the VTI is something of an orange in comparison.
Going through their Vanguard page tabs, there's effectively nothing that addresses how they approach distributions and capital gains on the Overview, Price and Performance, Fees and Minimums, or News and Reviews pages. The VTI and VTSAX portfolio and management pages include a line on turnover (irrelevant to us, as mentioned previously in this thread), VFIFX just has a list of the funds included.
The page that's significant for this topic is Distributions. On that page, it lists the distributions for the last year, type (Dividend or Cap Gain), date, and amount per share. All of the values are given in dollars and cents. So, to begin with I have to do math, on each fund in my portfolio, without any future predictability, to see what these dividends actually mean for me tax-wise.
Below that, we have a chart for Realized / Unrealized Gains, that includes a "realized capital gains as percent of Net Asset Value," line. For VFIFX, it's 10.13% as of 30 November. For VTI and VTSAX both, it's -.90%. What's frustrating is that they don't list historic averages, and I can't find the numbers for 2020 on any of the other sites either. I looked at the summary prospectus - nothing. I looked at the statutory prospectus - only this:
"Portfolio Turnover
The Fund may pay transaction costs, such as purchase fees, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in more taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the previous expense example, reduce the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 9% of the average value of its portfolio."
In the VTI prospectus? Exact same verbiage. No historic % NAV information, no historic realized / unrealized capital gains info, and here's the main point:
no information that makes it simple or logical for a retail investor to compare the probable capital gains impact of three of their own, very popular, funds. I'm sure Vanguard has constraints on how they can communicate tax information to customers. But I also think there's a pretty big gap between the information they have available now, and what they can publicize to retail investors trying to figure this out. I don't think it's too much to ask for, say, readily available (on their fund page) information on historic Capital Gain, Loss, and % of NAV, and perhaps a written statement on how the fund handles these requirements.