World Cup knockout qualifiers are the most exciting period of the football calendar outside of the World Cup itself. In a way, I was glad Australia finished 3rd in our Asian qualifying group meaning we have to go through 2 rounds of playoffs to make it to Russia 2018.
Conventional wisdom says it’s better to be home for the 2nd-leg
I was relieved we got the 2nd-leg home advantage. The accepted idea is that in the 2nd-leg you know exactly what result you need and you have a greater chance of determining the result at home than you would away.
On the other hand, some people counter that playing the 2nd-leg away is an advantage due to a combination of the away goals rule and the fact that more away goals are scored in 2nd-legs. Therefore, on average, the 2nd-leg away team gets more of an away goals bonus.
Also players who play their club football in the 1st-leg home country only have to travel once (from the 1st-leg to the 2nd-leg). Whereas players who play their club football in other counties have to travel twice (from where they play their club football to the 1st-leg and then from the 1st-leg to the 2nd-leg).
European club home and away ties
I wanted facts and found a lot of resources, including peer reviewed academic research, about the same question in regards to the UEFA Champions League 2-leg ties (and the previous versions of the same competition).
Overall studies and results show there is no advantage to playing the 2nd-leg at home. One older study disagrees and suggests that since the 1950s the 2nd-leg home team wins an adjusted 53% of ties. However, they find this advantage has become nonexistent in the last 20 years, which is what other studies suggest  .
World Cup intercontinental playoffs
That’s all well and good for European club football which often includes ties between teams from the same country. However, home advantage is more pronounced in intercontinental playoffs because the climatic differences, cultural differences and travel times are so much greater.
I compiled the data from all World Cup intercontinental playoffs. The results show the 2nd-leg home team qualifies 61% of the time. Of the 18 ties since 1958 the 1st-leg home team has won 7 and the 2nd-leg home team has won 11.
It’s a small sample size but it’s all there is. The recent trend is strong with 6 of the last 7 2nd-leg home teams qualifying.
Historical intercontinental playoff data
|World Cup||1st-leg home||2nd-leg home|
|2006||Trinidad and Tobago||Bahrain|
*Chile won this tie in a walkover. We do not award 2nd-leg home a point in this case.