Which ETF should I buy?

Screening Filters

1. Monthly Average Dollar Volume ≥ $500,000

   • Purpose: Ensure the ETF is sufficiently liquid and easy to trade.
   • Rationale: When someone asks “Which ETF should I buy?” without specifying niche preferences, it’s reasonable to assume they want something mainstream and practical. A minimum dollar volume filter helps:
     • Reduce the risk of wide bid–ask spreads (which increase trading costs).
     • Make it easier to enter and exit positions without moving the market.
     • Avoid obscure, thinly traded funds that may be harder for a typical investor to use.

2. Theme: Large Cap Blend Equities

   • Purpose: Focus on broad, core stock-market exposure rather than narrow or speculative themes.
   • Rationale: Large-cap blend equity ETFs typically:
     • Hold many of the biggest, most established companies (e.g., S&P 500–style exposure).
     • Mix growth and value (“blend”), giving balanced exposure instead of a style bet.
     • Serve well as a “core” holding for many investors, which is often what people mean when asking what ETF to buy.
       This aligns the screen with diversified, general-market funds rather than sector, thematic, or leveraged products.

3. Stock Position %: MoreThan90Pct

   • Purpose: Ensure the ETF is predominantly invested in stocks, not bonds, derivatives, or cash.
   • Rationale: The user did not ask for bond, commodity, or alternative ETFs. A >90% stock allocation:
     • Targets “true” equity ETFs, consistent with a broad stock-market exposure.
     • Avoids balanced or multi-asset funds that may not match someone simply seeking “an ETF to buy” for stock exposure.

4. Expense Ratio ≤ 0.05 (5 bps)

   • Purpose: Limit results to very low-cost ETFs.
   • Rationale: For broad equity ETFs, cost is one of the best predictors of long-term net performance:
     • Very low fees are a key attribute of the most widely recommended core ETFs.
     • Lower expenses mean more of the fund’s return stays in the investor’s pocket.
     • This filter steers away from niche, actively managed, or expensive products that may not be ideal as a default “which ETF should I buy?” answer.

5. Inception Date ≤ 2015-01-01 (at least ~10 years of history)

   • Purpose: Prioritize ETFs with a long track record and proven viability.
   • Rationale: When choosing a core ETF:
     • A longer history allows investors to see how it behaved across different markets.
     • Older funds tend to be larger, more stable, and less likely to be closed or merged.
     • This helps avoid very new products that have not yet proven their liquidity, tracking, or durability.

Why Results Match the User’s Question

• The user’s generic “Which ETF should I buy?” is interpreted as a request for solid, broadly diversified, mainstream equity ETFs suitable as a core holding.
• The combination of:
  • broad large-cap blend equity exposure,
  • high stock allocation,
  • good liquidity,
  • ultra-low fees, and
  • long operating history
    focuses the screen on exactly those types of widely used, high-quality core ETFs that professional analysts, financial planners, and long-term investors commonly consider when answering this kind of open-ended question.