The 2018 World Series was the fourth-lowest viewed Fall Classic ever. The 5-game series averaged just 14.39 million viewers, bettering only 2012 (12.64 million), 2008 (13.19 million), and 2014 (13.93 million).
Viewership only tells part of the story however. This year's series averaged the lowest 18-49 rating (3.69) since 2012 (3.6), and ratings in local major markets saw declines as well. In Boston, the series averaged a 34.6 rating over the course of five games, down 5 points from the 6-game series back in 2013, the last time the Red Sox were in the big game (39.6). The series-clinching game this year averaged a 43.2 rating in Boston, down a whopping 12 points from the local ratings of 2013's clinching game (55.2).
In Los Angeles (24.5), the game was down 4 points from just last year when the Dodgers were last in the series (28.5). The series-clinching game this year (26.0 in LA) was down more than 10 points from last year's game 7 (36.7). Also of note, the series is struggling to retain or grow viewing among younger people. The median age this year was the oldest on-record, averaging 56.2 years, up over a year from 2017 (55.0), and almost three years from 2016 (53.6). The last time the series averaged under 50 years old was all the way back in 2007 (49.9).
Detailed game-by-game ratings for the past six World Series' are provided below. Individual game men 18-49 ratings and median age data were unavailable for 2013 and 2014, but the overall average for each is provided.
2018 World Series:
| SHOW | Boston Rating | LA Rating | A 18-49 | M 18-49 | Med. Age | Viewers (millions) |
| World Series Game 1 (Fox) | 35.1 | 24.8 | 3.69 | 4.8 | 55.6 | 13.814 |
| World Series Game 2 (Fox) | 33.7 | 22.1 | 3.35 | 4.2 | 56.4 | 13.508 |
| World Series Game 3 (Fox) | 30.3 | 25.0 | 3.40 | 4.2 | 56.3 | 13.302 |
| World Series Game 4 (Fox) | 30.5 | 24.7 | 3.34 | 4.1 | 57.1 | 13.615 |
| World Series Game 5 (Fox) | 43.2 | 26.0 | 4.66 | 5.7 | 55.4 | 17.695 |
| Average | 34.6 | 24.5 | 3.69 | 4.6 | 56.2 | 14.387 |
| SHOW | Houston Rating | LA Rating | A 18-49 | M 18-49 | Med. Age | Viewers (millions) |
| World Series Game 1 (Fox) | 28.6 | 24.2 | 3.92 | 4.95 | 55.2 | 14.968 |
| World Series Game 2 (Fox) | 30.0 | 27.5 | 4.18 | 5.37 | 55.1 | 15.483 |
| World Series Game 3 (Fox) | 33.3 | 24.2 | 3.88 | 4.67 | 56.3 | 15.676 |
| World Series Game 4 (Fox) | 32.6 | 23.3 | 3.66 | 4.5 | 56.8 | 15.400 |
| World Series Game 5 (Fox) | 32.8 | 32.9 | 5.31 | 6.65 | 53.8 | 18.940 |
| World Series Game 6 (Fox) | 41.8 | 30.9 | 6.02 | 7.46 | 54.8 | 22.290 |
| World Series Game 7 (Fox) | 47.1 | 36.7 | 8.17 | 9.92 | 53.0 | 28.240 |
| Average | 35.2 | 28.5 | 5.02 | 6.22 | 55.0 | 18.714 |
2016 World Series:
| SHOW | CHI Rating | CLE Rating | A 18-49 | M 18-49 | Med. Age | Viewers (millions) |
| World Series Game 1 (Fox) | 34.1 | 46.5 | 5.57 | 7.1 | 53.2 | 19.369 |
| World Series Game 2 (Fox) | 35.4 | 38.9 | 4.76 | 5.8 | 54.1 | 17.393 |
| World Series Game 3 (Fox) | 35.1 | 39.2 | 5.19 | 6.2 | 54.7 | 19.385 |
| World Series Game 4 (Fox) | 30.1 | 39.8 | 4.23 | 5.1 | 55.4 | 16.705 |
| World Series Game 5 (Fox) | 42.8 | 48.6 | 6.73 | 8.1 | 53.8 | 23.639 |
| World Series Game 6 (Fox) | 40.2 | 40.5 | 6.62 | 7.4 | 53.5 | 23.398 |
| World Series Game 7 (Fox) | 51.2 | 48.6 | 12.62 | 14.9 | 50.5 | 40.047 |
| Average | 38.4 | 43.2 | 6.53 | 7.8 | 53.6 | 22.848 |
2015 World Series:
| SHOW | NYC Rating | KC Rating | A 18-49 | M 18-49 | Med. Age | Viewers (millions) |
| World Series Game 1 (Fox) | 26.2 | 57.3 | 4.6 | 6.0 | 52.7 | 14.944 |
| World Series Game 2 (Fox) | 21.3 | 56.6 | 3.9 | 4.9 | 53.8 | 13.722 |
| World Series Game 3 (Fox) | 23.1 | 48.0 | 3.2 | 4.0 | 56.5 | 13.205 |
| World Series Game 4 (Fox) | 25.6 | 47.5 | 3.4 | 4.1 | 56.5 | 13.587 |
| World Series Game 5 (Fox) | 25.5 | 60.0 | 5.1 | 6.3 | 53.5 | 17.206 |
| Average | 24.3 | 53.9 | 4.1 | 5.1 | 54.6 | 14.533 |
| SHOW | SFO Rating | KC Rating | A 18-49 | M 18-49 | Med. Age | Viewers (millions) |
| World Series Game 1 (Fox) | 29.3 | 48.2 | 3.4 | 4.8 | 55.7 | 12.191 |
| World Series Game 2 (Fox) | 28.7 | 49.7 | 3.4 | 12.917 | ||
| World Series Game 3 (Fox) | 26.4 | 49.0 | 3.1 | 12.130 | ||
| World Series Game 4 (Fox) | 28.9 | 43.6 | 2.6 | 10.742 | ||
| World Series Game 5 (Fox) | 34.1 | 48.0 | 3.3 | 12.635 | ||
| World Series Game 6 (Fox) | 27.7 | 54.6 | 3.5 | 13.330 | ||
| World Series Game 7 (Fox) | 38.8 | 58.3 | 6.6 | 23.517 | ||
| Average | 30.6 | 50.2 | 3.7 | 13.923 |
2013 World Series:
| SHOW | Boston Rating | St. Louis Rating | A 18-49 | M 18-49 | Med. Age | Viewers (millions) |
| World Series Game 1 (Fox) | 39.7 | 36.0 | 4.25 | 5.4 | 54.2 | 14.400 |
| World Series Game 2 (Fox) | 37.3 | 42.0 | 3.63 | 13.429 | ||
| World Series Game 3 (Fox) | 32.4 | 37.2 | 3.26 | 12.473 | ||
| World Series Game 4 (Fox) | 34.7 | 46.7 | 4.60 | 15.975 | ||
| World Series Game 5 (Fox) | 38.5 | 43.8 | 4.14 | 14.446 | ||
| World Series Game 6 (Fox) | 55.2 | 37.9 | 5.71 | 19.178 | ||
| Average | 39.6 | 40.6 | 4.25 | 14.984 |
Source: Nielsen Media Research