What are the HFA factors that may affect NFL betting?

What are the HFA factors that may affect NFL betting?

By Mark Taylor Sep 4, 2014

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Home Field Advantage (HFA) is a known phenomenon in sport and the NFL is no different. This NFL betting strategy article indicates a number of differing HFA factors bettors should consider before betting against the spread.

Home field advantage is an ever-present phenomenon in all-professional sports. In the NFL home sides have won 57.5% of all games by an average margin of 2.64 points since the league adopted its present 32-team format in 2002.

Unsurprisingly, a simple strategy of indiscriminately siding with home teams fails to produce a long-term profit when betting against the spread (ATS).

Seasons can see home sides do slightly better or worse than the norm, just through unpredictable, natural variation. For example, in 2013 home sides won nearly 60% of straight up bets and nearly 53% ATS, but since 2002 the overall against the spread success for home teams is just slightly above 49%.

Click here to read which NFL teams have the biggest HFA.

What causes Home Field Advantage?

Few subjects have caused more discussion than HFA, with numerous plausible explanations being put forward, often backed up by anecdotal or data driven proof.

However, such a universal trait is very unlikely to have a single cause and factors that may drive one side’s HFA may be entirely absent from that of another.

Familiarity In home surroundings

This assumes that players feel more comfortable playing in familiar surroundings and therefore, perform better.

I‘ve looked at the performance of Premier League and football league soccer teams in the years just before a move to a new ground and immediately afterwards. And it appeared to take a side three seasons before their home performance in their new surroundings recovered to pre move levels.

Research has also shown that home players produce an elevated level of natural testosterone when defending their own territory in home games and this is obviously important in sports that combine both skill and aggression, such as the NFL.

Games between divisional rivals have also shown slightly reduced HFA, possibly as a result of their regularity that increases the travelling team’s familiarity with both venue and opponent.

The NFL, unlike soccer has a variety of indoor and outdoor venues and different playing surfaces. A side may be built to suit their home environment, but this may lead to a disproportionate drop in performance on the road in less favourable conditions.

Therefore it appears that Home field advantage is as much a measure of road field disadvantage.

Travel considerations

HFA in English soccer has been in steady decline for many decades and many have attributed this to more luxurious travel arrangements. However, comfort is only one aspect of travelling.

The NFL can find sides shifting three time zones and with athletic ability appearing to peak in the late afternoon, sides may meet in very different stages of their circadian cycle.

The most obvious example of such match ups occur when the West Coast, Pacific zone teams – San Diego, Seattle, SF and Oakland – travel to the Eastern zone to play an early, one o’clock match.

The body clock of the West Coast teams at kick off is 10am, well short of the late afternoon peak and their game day preparations will have begun around 6am according to their circadian rhythm.

Some analysts also include Denver and Arizona from the adjacent Mountain zone as disadvantaged early risers on the road and the straight up record of all such sides in early East Coast games since 2003 is just over 30% straight up and 44% against the spread.

In common with many strategies that become public knowledge, betting the East Coast team hosting a West Coast side in an early game appears to be no longer profitable, as they have only covered the spread 51% of the time since 2009, even with a decade high peak in 2010.

The differences in the circadian rhythms of each team does open up the intriguing betting possibility that night games involving Pacific teams in the Eastern time zone may reverse the advantage. The visitors’ body clocks will be at the time of peak performance and their hosts will be well past it, especially in the 4th quarter.

Unfortunately, such 8pm games are relatively rare and although the Pacific and Mountain teams are 12 from 21 (57%) against the spread in night games in the Eastern zone since 2003, sample sizes should invite caution. A true 50/50 proposition would still produce results at least as extreme as this in around a third of such trials.

Sub consciously biased officiating 

This is a prime contender as a major factor in HFA. Vociferous home support has been associated with a tendency for referees to award decisions more generously to the home team, as well as more injury time when the home team is trailing in soccer.

Officials in the NFL also throw more penalty flags on the visiting side, an average of 6.4 per game compared to 5.9 for the hosts during the 2013 regular season.

For a side with a larger net gain for penalties – especially those that lead to a first down – the greater the likelihood that they have won the game. So conceding fewer penalties than your opponent is advantageous.

Instant replay reversals appear to show that visiting sides are more harshly treated compared to the home team, a situation officials may be forced to address. However, there may be situations where this apparent penalty flag bias is justified.

Increased crowd noise can induce penalties, such as false starts. In contrast, crowds are respectfully quiet when their offense is on the field, allowing down field players a cleaner release, which may lead to more downfield defensive infringements.

Also trailing sides, which will often be the visitors, may be forced to play closer to the edge of legality. These factors may persistently raise the visitor’s penalty count and help the host perform better at home.

Bettors should consider these factors that impact an NFL teams HFA, but remember there is no universal handicap, and must use this knowledge to create their own handicap values – after all, each team’s HFA can be influenced by a number of differing factors.

Mark Taylor is a freelance soccer and NFL writer who, along with producing expert content for Pinnacle Sports, also runs his own soccer analytics blog, the Power of Goals.

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