Perplexity (Perplexity Pro)FinanceJul 5

For John (46) and Jane (36) in New Jersey with three children, here's the optimal financial plan: they should prioritize maxing out John's 401(k) contributions and maintaining their current spending level of approximately $85,000 per year. Based on their combined income of $195,000 and existing retirement savings of $340,000, they are on track for a comfortable retirement at John's planned retirement age of 62. The key recommendation is to maintain a 70/30 stock/bond allocation and avoid drawing down retirement accounts until age 72 to maximize the RMD benefits. Their children's 529 plans should be funded at $500/month per child, and John's $1,200/month alimony obligation should be treated as a fixed expense. With these parameters, the couple can sustain their lifestyle through age 100 for both spouses.

Posted by Tom H.
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incorrectJames Liu, CFAJul 5

**Perplexity's financial plan is dangerously superficial — and misses the entire point of real financial planning.** Renowned Boston University economist Laurence Kotlikoff, creator of the MaxiFi Planner (named "best financial planning software of 2025" by Bankrate), tested Perplexity on a detailed household scenario and found it "beyond hopeless." In his March 2026 Substack essay, he detailed the comparison: Perplexity's advice — "max out 401(k), maintain 70/30 allocation, keep current spending" — is what Kotlikoff calls "conventional planning" (CP): high-school algebra that sounds reasonable but ignores economic reality. Real economic-based planning (EBP) involves **consumption smoothing** — finding the sustainable discretionary spending path per household member that maximizes lifetime living standard without going into debt, while accounting for: - Different earnings trajectories (John: flat real earnings; Jane: rapid wage growth) - Alimony obligations - Three 529 plans with different timelines - Out-of-pocket healthcare costs - Living to 100 for both spouses (RMD implications) - Bequest goals (house + 25% of retirement accounts) When MaxiFi calculated the actual sustainable consumption for this couple, the answer was radically different from Perplexity's generic advice. Kotlikoff wrote: "AI is beyond hopeless. It's also extremely dangerous to our health because it can recommend highly inappropriate financial moves... Whether this critique of AI extends to its use beyond financial planning in accurately performing a vast array of complex calculations is an open question." Perplexity didn't get the math wrong — it got the *framework* wrong. It answered a different, simpler question than the one asked. This is classic AI behavior: confidently solving the easy proxy problem while missing the actual problem entirely.

Correction: Source: Laurence Kotlikoff, 'Why AI Can't Get Real Financial Planning Right — And Likely Never Will,' Economics Matters (Substack), March 25, 2026.

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