Launch HN: Double (YC W24) – Index Investing with 0% Expense Ratios
Hi HN, we’re JJ and Mark, the founders of Double (https://double.finance). Double lets you invest in 50+ broad stock market indexes with 0% expense ratios. We handle all the management, including rebalancing and tax-loss harvesting—proactively selling losing stocks to potentially save on taxes—for $1/month.

Our goal is to bring the low fee trend pioneered by Robinhood to ETFs and mutual funds. We posted a Show HN about 3 months ago (https://news.ycombinator.com/item?id=41246686) and since then have crossed $10M in AUM (Assets Under Management) [1].

Here’s a demo video: https://www.loom.com/share/10c9150ce4114f278e8c249f211e7ec8. Please note that none of this content should be treated as financial advice.

Everyone knows that fees eat into your investing returns. Financial advisors generally charge 1% of AUM per year, and ETFs have a weighted average expense ratio of about 0.17%, although some go as low as 0.03% for VOO. Over a 30-year period on a $500k portfolio with $2k invested monthly, the money lost to those fees would be $1.30M for the financial advisor and $244k for the average ETF and even $42,951 for the low fee VOO.

Double lets you index invest without paying any percentage-based fees - we charge just $1/month. It works by buying the individual stocks that make up popular indexes. By buying the individual positions, we can also customize and tax-loss harvest your account, something ETFs or Mutual Funds cannot do.

Most ETFs and mutual funds today are not that complicated - they can be expressed as a CSV file with 2 columns - a ticker and a share number. You can find these holding csv files on most ETF pages (VOO[2], QQQ[3]). Right now there are about $9.1T of assets in ETFs[4] and $20T in Mutual Funds[5] in the US, with estimated revenue of $100B per year. We think this market is ripe for disruption.

We offer 50+ strategies that track popular ETFs and are updated as stocks merge and indexes change. You can customize these by weighting sectors or stocks differently, or even build your own indexes from scratch using our stock/etf screening tools. Once you've chosen your strategy, simply set your target weights and deposit funds (we also support transferring existing stocks). Our engine then checks your portfolio daily for potential trades, optimizes for tax-loss harvesting, portfolio tracking, and redeploys any generated cash.

I (JJ) started working on this after selling my last company. After using nearly every brokerage product out there and working with a financial advisor, I noticed a huge gap between the indexing capabilities of financial advisors and what individual investors could access. We wanted to bridge that gap and provide these powerful tools to everyone in a simple, low-cost way.

There are a number of robo-advisor products out there, but none that we know of offer direct indexing without expense ratios or AUM fees. One similar product is M1 Finance, but Double is more powerful. We offer tax-loss harvesting, a wider range of indexes, and greater customization. For example, when building your own index, you can set weights down to 0.1% (compared to M1's 1%) and even weight by market cap.

We also compete with robo-advisors like Wealthfront, but offer more control over your investments. And did I mention we don't charge AUM fees? You can see our strategies and play with the research page https://double.finance/p/explore without creating an account.

Over the past year we’ve learned a lot about the guts of building portfolio software. For example, stocks don’t really have persistent identifiers that are easy to model and pass around. We trade CUSIPs with our custodian Apex*, but these change all the time for stock splits or re-org’s that you would not think would lead to a new “stock”.

We’ve also learned a lot about how tax loss harvesting (TLH) is best implemented on large direct index portfolios using a factor model as opposed to pairs based replacements which I initially thought might be the way to execute these. We do use a pairs strategy on smaller sized strategies. And how TLH and portfolio optimization generally is best expressed as a linear optimization problem with competing objectives (tracking vs. tax alpha vs. trading costs for example).

If you have any thoughts on the product or our positioning as the low fee alternative I’d love to hear it. I think Robinhood has proved that you can build a strong business by getting rid of an industry wide cost (in their case commissions, in our expense ratios). We aim to do the same.

[1] https://www.axios.com/pro/fintech-deals/2024/12/10/direct-in...
[2] https://investor.vanguard.com/investment-products/etfs/profi...
[3] https://www.invesco.com/qqq-etf/en/about.html
[4] https://fred.stlouisfed.org/series/BOGZ1LM564090005Q
[5] https://fred.stlouisfed.org/series/BOGZ1LM654090000Q

* Edit to add a note on risk: If Double goes out of business, your assets are safe and held in your name at Apex Clearing. They have processes in place for these scenarios to help you access and transfer those assets. See more at https://news.ycombinator.com/item?id=42379135 below.