In football, a coin toss determines who starts with possession of the ball first. The away team is asked by the head referee to pick heads or tails. Following the result of the coin toss, the team who wins the toss has 3 options to choose from. They can either receive, kick, or defer. To defer in football is to withhold the decision to receive or kick until the start of the 2nd half.
When a team defers the choice of whether to receive or kick at the coin toss, the other team has to choose whether they want to kick or receive first or pick the side they will play on. At the start of the second half, the team that elected to defer is given the following options:
If a team chooses to defer, they will almost always choose to receive in the second half. Otherwise, they would be at a big disadvantage as their opponent would receive the ball to start both halves.
Deferring the first half coin toss is a strategy that many teams employ. While there is no concrete statistical proof that deferring on a kickoff results in more victories, many coaches still swear by it. They believe that it offers a psychological advantage as well as more possessions in the second half. The thought is that the more possessions a team has in the more important half (second) the better chance they have at winning. There are not many cons to deferring as you guarantee yourself getting the ball at half. The only con may be that the other team has the opportunity to set the tone and score first, forcing your team to climb out of a deficit early on.
In overtime teams are unable to defer as the extra 10 minute quarter is played in a sudden death format. Therefore, there is no second half to save your option to receive or kick. There are limited reasons why a team would elect to kick first in overtime after winning the toss because the team to score a touchdown first wins the game. Unless a team feels they have a better chance of scoring a defensive touchdown than an offensive touchdown, it always makes sense to receive the ball if you win the coin toss in overtime. Statistically speaking, teams that elect to receive the ball first win 55% percent of the time, so teams rarely elect to kick.
Before 2008 teams only had two options after winning the coin toss to start the game: pick the side they would like to defend or decide whether they wanted to kick or receive the ball. Therefore, if a team won the toss they ultimately had to elect to receive otherwise the other team would get the ball to start the game as well at the beginning of the second half. That would explain why 99.6% of teams who won the coin toss from 1999-2007 elected to receive the ball. In 2008 the option to defer was added as a choice. Instead of being made to select whether you wanted to receive or kickoff, a team could save their choice for the second half. At first, most teams would often choose to receive the ball with only 32% electing to defer in the first year deferring was allowed. However, head coach Bill Bellicheck of the New England Patriots changed the way coaches thought about coin tosses by almost always choosing to defer. The Patriots had great success this way, often able to score late in the first half and at the beginning of the second half for a 2 for 1. Now around 92% of teams defer when winning the coin toss.
Deferring the kickoff in football has become somewhat of a norm as the majority of teams are electing to wait until the second half to receive the ball after winning the initial coin toss. Over the course of the past 13 seasons since the option to defer was introduced in 2007, there has been a dramatic increase in the percentage of teams that elect to defer after winning the coin toss. At first teams were still electing to receive or kick and were unsure about deferring as only 39% of teams elected to defer in 2007. It wasn't until 2012 when the defer option was selected more times than the receive option. As of 2018, 92% of teams that win the coin toss elect to defer. That being said, some teams still elect to receive most of the time such as the Dallas Cowboys who have only chosen to defer 26% of the time over the span of 2008 to 2018. Contrastly, the Patriots have elected to defer 95% of the time during that same span.
While there is no definitive answer to this question, there are a few possibilities. Coaching strategy has changed throughout the years in the NFL. Offenses have become increasingly better as time has gone on making each possession more important because of the necessity to score. Coaches may feel there is a distinct advantage to getting the ball to begin the half with the option to make adjustments during the halftime period having seen a full half of the other team's defensive strategy. Another possibility is that when a team defers the other team has to elect to receive the ball unless they want the other team getting the ball twice, leaving the choice of which side the teams will play on in the hands of the team that won the toss initially. Therefore, instead of just getting the ball and not having a say in direction of play, the defer option allows for teams to get the ball at half as well as decide what side they want to play on.This can be very important in games in which there is a lot of wind because teams will strategize the side they chose making sure they are kicking into the wind in the 4th quarter.
When a team defers, the other team essentially has the same options as the team who won the toss. They can elect to kick, receive, or choose which side to play on. Most will elect to receive because the other team will have the option to receive the ball starting the second half. Rarely would this ever happen, but if a team elects to defer the coin toss and the other team elects to kick or pick a side, the team who elected to defer can end up with the ball twice (to begin the game as well as at the beginning of the second half). In almost all cases, the team who defers the initial coin toss will receive the ball to begin the second half.