U.S. television ratings
Seasonal rankings (based on average total viewers per episode) of American Idol. It holds the distinction of having the longest winning streak in the Nielsen annual television ratings; it became the highest-rated of all television programs in the United States overall for an unprecedented seven consecutive years, or eight consecutive (and total) years when either its performance or result show was ranked number one overall.
Each U.S. network television season starts in late September and ends in late May, which coincides with the completion of May sweeps.
American Idol premiered in June 2002 and became the surprise summer hit show of 2002. The first show drew 9.9 million viewers, giving Fox the best viewing figure for the 8.30 pm spot in over a year. The audience steadily grew, and by finale night, the audience had averaged 23 million, with more than 40 million watching some part of that show. That episode was placed third amongst all age groups, but more importantly it led in the 18–49 demographic, the age group most valued by advertisers.
The growth continued into the next season, starting with a season premiere of 26.5 million. The season attracted an average of 21.7 million viewers, and was placed second overall amongst the 18–49 age group. The finale night when Ruben Studdard won over Clay Aiken was also the highest-rated ever American Idol episode at 38.1 million for the final hour. By the third season, the show had become the top show in the 18–49 demographic a position it has held for all subsequent years up to and including the tenth season, and its competition stages ranked first in the nationwide overall ratings. By the fourth season, American Idol had become the most-watched series amongst all viewers on American TV for the first time, with an average viewership of 26.8 million. The show reached its peak in the fifth season with numbers averaging 30.6 million per episode, and this season remains the highest-rated of the series.
The sixth season premiered with the series' highest-rated debut episode and a few of its succeeding episodes rank among the most-watched episodes of American Idol. During this time, many television executives began to regard the show as a programming force unlike any seen before, as its consistent dominance of up to two hours, two or three nights a week, exceeded the 30- or 60-minute reach of previous hits such as NBC's The Cosby Show. The show was dubbed "the Death Star", and competing networks often rearranged their schedules in order to minimize losses. However, the sixth season also showed a steady decline in viewership over the course of the season. The season finale saw a drop in ratings of 16% from the previous year. The sixth season was the first season wherein the average results show rated higher than the competition stages (unlike in the previous seasons), and became the second-highest-rated of the series after the preceding season.
The loss of viewers continued into the seventh season. The premiere was down 11% among total viewers, and the results show in which Kristy Lee Cook was eliminated delivered its lowest-rated Wednesday show among the 18–34 demo since the first season in 2002. However, the ratings rebounded for the seventh-season finale with the excitement over the battle of the Davids, and improved over the sixth season as the series' third most watched finale. The strong finish of season seven also helped Fox become the most watched TV network in the country for the first time since its inception, a first ever in American television history for a non-Big Three major broadcast network. Overall ratings for the season were down 10% from the sixth season, which is in line with the fall in viewership across all networks due in part to the 2007–2008 Writers Guild of America strike.
The declining trend however continued into the eighth season, as total viewers numbers fell by 5–10% for early episodes compared to the seventh season, and by 9% for the finale. In the ninth season, Idol's six-year extended streak of perfection in the ratings was broken, when NBC's coverage of the 2010 Winter Olympics on February 17 beat Idol in the same time slot with 30.1 million viewers over Idol's 18.4 million. Nevertheless, American Idol overall finished its ninth season as the most watched TV series for the sixth year running, breaking the previous record of five consecutive seasons achieved by CBS' All in the Family and NBC's The Cosby Show.
In the tenth season, the total viewer numbers for the first week of shows fell 12–13%, and by up to 23% in the 18–49 demo compared to the ninth season. Later episodes, however, retained viewers better, and the season ended on a high with a significant increase in viewership for the finale – up 12% for the adults 18–49 demographic and a 21% increase in total viewers from the ninth-season finale. While the overall viewer number has increased this season, its viewer demographics have continued to age year on year – the median age this season was 47.2 compared to a median age of 32.1 in its first season. The demographics also became "whiter" over time and less diverse. Nevertheless, in the 2010–11 television season, Fox maintained its lead on over other networks with its seventh consecutive season of victory overall in the 18–49 demographic ratings in the United States.
The eleventh season, however, suffered a steep drop in ratings, a drop attributed by some to the arrival of new shows such as The Voice and The X Factor. The ratings for the first two episodes of the eleventh season fell 16–21% in overall viewer numbers and 24–27% in the 18/49 demo, while the season finale fell 27% in total viewer number and 30% in the 18–49 demo. The average viewership for the season fell below 20 million viewers the first time since 2003, a drop of 23% in total viewers and 30% in the 18/49 demo. For the first time in eight years, American Idol lost the leading position in both the total viewers number and the 18/49 demo, coming in second to NBC Sunday Night Football, although the strengths of Idol in its second year in the Wednesday-Thursday primetime slots helped Fox achieve the longest period of 18–49 demographic victory in the Nielsen ratings, standing at 8 straight years from 2004 to 2012.
The loss of viewers continued into the twelfth season, which saw the show hitting a number of series low in the 18–49 demo. The finale had 7.2 million fewer viewers than the previous season, and saw a drop of 44% in the 18–49 demo. The season viewers averaged at 13.3 million, a drop of 24% from the previous season. The thirteenth season suffered a huge decline in the 18–49 demographic, a drop of 28% from the twelfth season, and American Idol lost its Top 10 position in the Nielsen ratings by the end of the 2013–14 television season for the first time since its entry to the rankings in 2003 as a result, and never regained its Top 10 position by the series' end in 2016.
The continuing decline influenced further changes for the fourteenth season, including the loss of Coca-Cola as the show's major sponsor, and a decision to only broadcast one, two-hour show per week during the top 12 rounds (with results from the previous week integrated into the performance show, rather than having a separate results show). On May 11, 2015, prior to the fourteenth-season finale, Fox announced that the fifteenth season of American Idol would be its last. Despite these changes, the show's ratings would decline more sharply. The fourteenth-season finale was the lowest-rated finale ever, with an average of only 8.03 million viewers watching the finale. The show's ratings, however, rebounded in its final season and ended its run in 2016 as Fox's first-ever program to conclude its run without dropping from the Nielsen Top 30 most-watched television shows in each of its seasons.
For the revived series on ABC, the ratings were lower but remained stable compared to previous seasons on Fox. The finale of the seventeenth season was slightly more watched than the sixteenth.