How high adjustment costs change savings

What if your biggest investment risk isn't the stock market—but your own income?

In this episode, we are joined by Patrick Adams, a PhD candidate at MIT, for a fascinating deep dive into how income risk, spending commitments, and liquidity constraints reshape what "optimal" investing actually looks like. Drawing on large-scale administrative tax data, Patrick challenges the conventional wisdom that young investors should be heavily—or even fully—invested in equities.

We explore why stocks appear safe over long horizons but become risky when real-world constraints force investors to sell at the worst possible times. Patrick explains how high-income households behave during market downturns, why their income risk is closely tied to stock market performance, and how consumption commitments like mortgages and childcare create hidden financial leverage. The conversation also introduces a new life-cycle model that incorporates these frictions—leading to surprisingly conservative optimal equity allocations for working-age investors. This episode reframes asset allocation as a problem of liquidity and risk management, not just return maximization.

Key Points From This Episode:

(0:00:00) Introduction to the podcast and overview of the episode's focus on asset allocation and new research.

(0:01:18) Patrick Adams' background, MIT PhD research, and how the paper was discovered.

(0:07:08) Why stocks are considered safe for long-term investors based on historical returns.

(0:08:37) When the "stocks for the long run" logic breaks down—forced selling during downturns.

(0:10:35) Evidence: High-income households sell stocks during crashes instead of buying.

(0:12:24) Data source: Administrative U.S. tax return data and its advantages/limitations.

(0:14:23) Investors shift into fixed income during crashes rather than staying invested.

(0:16:52) Financial reality: High wealth, but low liquid assets relative to income.

(0:18:00) Human capital: Income is risky and correlated with stock market downturns.

(0:20:15) Typical allocation: About 25% of liquid wealth in stocks for working-age households.

(0:22:36) Higher-income households have more volatile flows and greater exposure to stock risk.

(0:23:42) Income shocks drive stock selling—not just panic or behavioral mistakes.

(0:25:29) Why households draw down assets instead of cutting spending sharply.

(0:27:26) Consumption commitments (mortgages, childcare) act like hidden leverage.

(0:27:57) Key risk factors: Income volatility, low liquidity, and inflexible expenses.

(0:31:31) Traditional models vs reality: People don't cut spending—they use savings.

(0:35:25) New model incorporates income risk, market crashes, and spending frictions.

(0:38:33) Core finding: Optimal equity allocation for working-age investors is only 10–40%.

(0:40:55) Practical takeaway: Asset allocation is fundamentally about emergency funds.

(0:42:35) Higher fixed expenses require larger safe asset buffers.

(0:43:49) Counterintuitive result: Retirees may optimally hold more equities than workers.

(0:46:56) Scenario analysis: Selling during downturns destroys long-term returns.

(0:49:12) Key drivers of results: Income-stock correlation and spending rigidity.

(0:51:11) Why this model differs from others suggesting 100% equity portfolios.

(0:53:20) When 100% equity could make sense: low risk, high wealth, high risk tolerance.

(0:56:28) Personal impact: Patrick rethinks his own savings, risk, and spending commitments.

(0:57:34) Advice for listeners: Focus on liquidity, income risk, and fixed expenses.

(0:59:58) Defining success: Impactful research, teaching, and meaningful personal relationships.

Links: Patrick Adams – MIT PhD Candidate: https://patrick-adams.com/

Meet with PWL Capital: https://calendly.com/d/3vm-t2j-h3p

Rational Reminder on iTunes — https://itunes.apple.com/ca/podcast/the-rational-reminder-podcast/id1426530582. Rational Reminder on Instagram — https://www.instagram.com/rationalreminder/

Rational Reminder on YouTube — https://www.youtube.com/channel/ Benjamin Felix — https://pwlcapital.com/our-team/

Benjamin on X — https://x.com/benjaminwfelix

Benjamin on LinkedIn — https://www.linkedin.com/in/benjaminwfelix/

Cameron Passmore — https://pwlcapital.com/our-team/

Cameron on X — https://x.com/CameronPassmore

Editing and post-production work for this episode was provided by The Podcast Consultant (https://thepodcastconsultant.com)