2018 Predictions — Accuracy and Score

David Manheim
6 min readJan 12, 2019


Medium is now gated. I’ve moved. Non-gated post replacement link.

OK, it’s (slightly after) that time of year again, and I need to make my new predictions. But you can’t improve unless you figure out how you’ve been doing, so here’s my review of last year’s predictions. (I still need to put in my calibration numbers, and those aren’t looking great for me.)

Note: The first set are my own, the second (numbered) set are following Scott Alexander’s predictions. I have the outcome as a binary yes/no in bold preceding the question. I have removed many of my earlier comments, and added new ones in bold. Feel free to go back and make sure I’m not cherry picking to make myself look less stupid.

(I’m taking out the long-term predictions that I can’t yet grade.)

Brier Score: 0.1957. Ouch! (Brier Score w/o Crypto Qs: 0.1374 But listing this score is just me cheating to feel better.)

My calibration was fairly good, though the sample is noisy.
Key: Right / Wrong [Cheating, w/o Crypto] (Cumulative w/ 2017) — Percentage [Cheating, w/o Crypto] (Cumulative)

[50–60%): 4 (6) / 1 (4) — 80% (60%)
[60–70%): 3 (11) / 4 (7) — 43% (61%)
[70–80%):4 (10) / 0 (2) — 100% (83%)
[80–90%): 5 [3] (15) / 3 [1] (4) — 57% [75%] (79%)
[90–95%):4 (13) / 0 (0) — 100% (100%)
[95–99%):7 (18) / 2 [0] (2) — 78%[100%] (90%)
[99+%]: 0 (4) / 0 (0) — N/A (100%)

US Politics

No — Democrats take the senate: 45%
(The seats up for grabs are largely Democrat controlled — hard to make inroads.)

No — The Republicans will maintain control of the House of Representatives in 2018 elections: 45%
(Last year I said 40% — this is what the prediction markets now say, but I’m updating. I’m skeptical that Trump’s unpopularity convinces the heartland to vote dem, or stay home. But this is a low confidence prediction, made early.)

No (Wrong)— Republicans win House of Representatives special election in Pennsylvania’s 18th district: 60%

Yes/No — Trump’s approval rating, based on the RCP average, will be over 40% / 45% at some point in 2018: 60% / 25% (It got really close to 45%, though.)


I SUCK AT THIS, as the past two years should make clear. (And if you think you can do better, why aren’t you rich? (Alfred, you don’t need to respond, I know.)) But I still think there’s a real chance that the bubbles pop — and even if they don’t, I expect the pace of growth to slow once the regular capital markets have put in their money.

Bitcoin Crashes — “loses more than 50% of peak value”;

Distribution — Hard to Score via Brier — Off-the cuff probability distribution:
10% — BTC investment (not use) spreads until much of public holds at these high prices before crashing
60% — not very soon, but w/in 2–3 years
15% — Crash During 2018
Yes — 15% — (Mid-December 2017) was the top.

I’m on the record already;
No, (No) — Conditional on the crash occurring? 1 year later, I’d predict bitcoin is smaller than at least 2 alternatives, and less than 25% of total cryptocoin market cap, with 80% confidence. (1 altcoin, 33%, 90% conf.)

Global Catastrophic Risks

AI Progress indicators -

AI wins a Real Time Strategy game (RTS — Starcraft, etc.) in full-mode against the best human players before end of;

(Other years removed.)

Scott’s Prediction Topics (His Numbers)

Yes — 1. Donald Trump remains president at end of year: 98% (95%)
Yes — 2. Democrats take control of the House in midterms: 55% (80%)
No— 3. Democrats take control of the Senate in midterms: 45% (50%)
No— 4. Mueller’s investigation gets cancelled (eg Trump fires him): 20% (50%) [I assume almost immediately being relaunched by appointing him an independent counsel or equivalent after firing doesn’t count. If it does, I probably agree with Scott.]
Correct— 5. Mueller does not indict Trump: 80% (70%) [I can’t see him indicting Trump. I think there will be a report with arguably indictable offenses, but even so it very well may come out in 2019.] ( I’m happy to have called what now seems inevitable in the comment.)
No — 6. PredictIt shows Bernie Sanders having highest chance to be Dem nominee at end of year: 60% (60%) [Biden and Warren are more viable choices, and Bernie is really old. But this is predicting the prediction, so I’m less certain about this than I am that he won’t be the nominee.] (Beto and Kamala Harris are on top. And given that Obama beat Hillary, I should have remembered that new people would show up. This was stupidly overconfident)
Yes — 7. PredictIt shows Donald Trump having highest chance to be GOP nominee at end of year: 95% (95%)
No— 9. Some sort of major immigration reform legislation gets passed: 80% (70%)
Correct— 10. No major health-care reform legislation gets passed: 90% (95%) (I predicted this right after the individual mandate was repealed at the end of 2017, it seems, so yeah.)
Correct- 11. No large-scale deportation of Dreamers: 95% (90%) (Not that they figured anything out, but it hasn’t been mass deportations.)
Correct — 12. US government shuts down again sometime in 2018: 60% (50%) (I was correct by a hair. )
Correct — 13. Trump’s approval rating lower than 50% at end of year: 95% (90%)
No. — 14. …lower than 40%: 60% (50%)
WAITING ON SCOTT — 15. GLAAD poll suggesting that LGBQ acceptance is down will mostly not be borne out by further research: 70% (80%) [This is WAY outside my wheelhouse, here.]

No (Correct) — 16. Dow does not fall more than 10% from max at any point in 2018: 45% (50%) (It did, twice!)
Wrong — 17. Bitcoin is higher than $5,000 at end of year: 90% (95%)
Wrong — 18. Bitcoin is higher than $10,000 at end of year: 70% (80%)
Right— 19. Bitcoin is lower than $20,000 at end of year: 80% (70%)
It was — 20. Ethereum is lower than Bitcoin at end of year: 50% (95%)
X — 21. Luna has a functioning product by end of year: N/A (90%) [I don’t know what this is.] (Still Don’t.)
X — 22. Falcon Heavy first launch not successful: N/A — Just saw this. (70%)
X — 23. Falcon Heavy eventually launched successfully in 2018: N/A — Just saw this. (80%)
Correct — 24. SpaceX does not attempt its lunar tourism mission by end of year: 95% (95%) [??]
Correct — 25. Sci-Hub is still relatively easily accessible from within US at end of year (even typing in IP directly is relatively easy): 95% (95%) [??]
Correct — 26. Nothing particularly bad (beyond the level of an funny/weird news story) happens because of ability to edit videos this year: 80% (90%) [But I’m putting a major fake news controversy as bad. Unsure Scott agrees.]
Nope — 27. A member of the general public can ride-share a self-driving car without a human backup driver in at least one US city by the end of the year: 60% (80%)

Correct — 28. Reddit does not ban r/the_donald by the end of the year: 90% (90%)
Correct — 29. None of his enemies manage to find a good way to shut up/discredit Jordan Peterson: 70% (70%) [??]

{I don’t follow these.}

PERSONAL (Not Scott’s, but adapted):
Correct — 47. I move by end of July: 95%
Correct— 50. I go to Oxford as a visiting researcher: 65% (It was AMAZING.)
Correct (I didn’t)— 51. I do a postdoc at Oxford: 30%
Nope — 53. I get at least one article published in a newspaper or decently large website (not Ribbonfarm or Kol Habirah): 20% (But it was close — I submitted something that’s still in process.)
55. I weigh more than 160lb at year end: 50% (Close. And I don’t have a scale handy. Not that it affects the score, so…?)
Correct — 63. My paper with Scott G. goes on Arxiv/published: 90%
N/A- 64. My paper with Abram/Osonde goes on Arxiv/published: 50% (To explain, this was intended to be the multi-agent goodhart paper, which I did put a version of online, and is getting jounral reviewed, but it is not co-authored with them, so I’m taking a mulligan.)