Forecasting Medals


Four years ago, I wondered how much home advantage improved the home host nation’s medal prospects at the Olympics, and being a professional analyst, I found that out, so since we’re about to go again, I thought I’d revisit it for 2016-here’s an updated version in which I estimate the number of gold medals GB and Brazil will win in Rio this summer.

The table below shows how a host nation fared medal-wise in the Olympics prior to hosting, the Olympics they hosted, and the Olympics after the one they hosted.

The entries refer to the gold medals and the overall medals. For example, China won 32 golds and 63 medals in all in Athens, 51 golds and 100 medals in all in Beijing, and 38 golds and 88 medals total in London. “Events” refers to the total number of events in the games in question.

Golds/ Medals
At previous Games At Hosted Games At Next Games Events
2012 Great Britain 19/47 29/65 300
2008 China 32/63 51/100 38/88 302
2004 Greece 4/13 6/16 0/4 301
2000 Australia 9/41 16/58 17/49 300
1996 USA 37/108 44/101 37/94 271
1992 Spain 1/4 13/22 5/17 260
1988 Korea Republic 6/19 12/33 12/29 241

What’s clear is that there is a marked improvement in performance (in raw number terms) when an Olympics is hosted, and, generally speaking, a drop at the following event.

Since the number of events changes in each games, it makes sense to take this into consideration. The below table shows the percentage of events at which the country in question won a gold medal. GB won 6.3% of available golds in Beijing, and 9.7% of golds in London. The “Home Factor” is the percentage of golds at the host Olympics divided by the percentage of golds at the previous Olympics. The “Away Factor” is the percentage of golds won at the Olympics following hosting divided by the percentage of golds won at the hosted Olympics.

Previous Gold Ratio Current Gold Ratio Next Gold Ratio Home Factor Away Factor
2012 Great Britain 6.3% 9.7% N/A 1.54
2008 China 10.6% 16.9% 12.1% 1.59 0.72
2004 Greece 1.3% 2.0% 0.0% 1.50 0.00
2000 Australia 3.3% 5.3% 5.6% 1.61 1.06
1996 USA 14.2% 16.2% 12.3% 1.14 0.76
1992 Spain 0.4% 5.0% 1.8% 12.05 0.37
1988 Korea Republic 2.7% 5.0% 4.6% 1.88 0.93

From this, we can see (barring the Spanish outliers- the huge increase is due mostly to their poor performance in Seoul), there is an uplift of about 1.56 in the number of golds won on home soil (that is, for every gold won in the previous Olympics, you will win 1.56 when you host). In fact, using this metric, Britain is doing very well even for a host nation. The future is a bit less clear. China (currently, though that may change) and Australia improved further in the Olympics after hosting, while the rest deteriorated, although still with higher medal tallies than before hosting, suggesting that being an Olympic host is good for legacy purposes (unless you’re Greece, it would seem).

In terms of total medals, the following table shows the same as above, except it is “total medals per event” (you could regard it as the percentage of events which featured at least one medalist from the country).

Previous Medal Current Medal Next Medal Home Factor Away Factor
2012 Great Britain 15.6% 21.7% N/A 1.39
2008 China 20.9% 33.1% 29.1% 1.58 0.88
2004 Greece 1.3% 2.0% 1.3% 1.50 0.66
2000 Australia 15.1% 19.3% 16.3% 1.28 0.84
1996 USA 41.5% 37.3% 31.3% 0.90 0.84
1992 Spain 1.7% 8.5% 6.3% 5.10 0.74
1988 Korea Republic 8.4% 13.7% 11.2% 1.63 0.81

We see roughly similar statistics to before, except that, remarkably, the USA seemed to do worse in Atlanta than in Barcelona. This could be due in part to this being the first Olympics to feature the plethora of states which gained independence from the former Yugoslavia and USSR (the more opponents you face, the more likely it is you won’t do so well).

Here, the home factor is roughly 1.4, meaning for every medal you get at the previous Olympics, you can expect 1.4 when you host. Again, Britain overperformed on this regard. The “next Olympics” numbers are a bit more consistent here, and suggest that for every medal you win when you host, you can expect 0.84 the next time, but this still represents an improvement on the Olympics before that, so hosting is good, at least on that front.

Extrapolating this to Rio, we can estimate that GB will win somewhere in the region of 19-22 golds and 50-60 medals total.

As for Brazil, they won 3 golds and 17 medals total in London, so using the above extrapolations, I would estimate about5-8 golds and 22-27 medals total, though there’s a caveat here that the numbers were quite small to begin with and are therefore more prone to large swings percentage-wise.

So, if you want to earn 50% more gold medals, host an Olympics. It’s that easy.

Other Olympics-based Stats are on the Financial Times website, which is AMAZING.

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