Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Good/Bad idea to have an ETF that encompasses another
Let's simplify things by assuming you only own 2 stocks. By owning VOO and VTI, you're overweight on large- and mid-cap stocks relative to the market composition. Likewise, by owning VTI and VT, you're overweight on U.S. stocks; conversely, by owning VXUS and VT, you're overweight on non-U.S. stocks. These are all perfectly fine positions to take if that's what you intend and have justification for. For example, if you're in the U.S., it may be a good idea to hold more U.S. stocks than VT because of currency risk. But 4 equity index ETFs is probably overcomplicating things. It is perfectly fine to hold only VTI and VXUS because these funds comprise thousands of stocks and thus give you sufficient diversification. I would recommend holding those 2 ETFs based on a domestic/international allocation that makes sense to you (Vanguard recommends 40% of your stock allocation to be international), and if for some reason you want to be overweight in large- and mid-cap companies, throw in VOO. You can use Morningstar X-Ray to look at your proposed portfolio and find your optimal mix of geographic and stock style allocation.