The first day of March Madness action is in the books.

Thursday didn't see any huge upsets, with No. 12 Murray State being the lowest-ranked team of the day to pull off a first-round win.

Despite this, brackets across the country were busted, as just 42,828 perfect brackets remained in ESPN's Tournament Challenge.

March Madness is the most unpredictable event in all of sports.

Though many contests through the years have advertised larger-than-life prizes, the quest for a "perfect bracket" that correctly predicts the winner of all 63 games of the tournament is an all but impossible endeavor that we are unlikely to see in our lifetimes.

Read more: The Cinderella team that rocked March Madness the year you were born

Case in point: After one day of March Madness action, just 0.25% of brackets in ESPN's Tournament Challenge remained perfect, according to ESPN Stats & Info. More than 17.2 million brackets were submitted to ESPN this year, and of them, only 42,828 nailed the first 16 games of the tournament on Thursday.

That low perfection percentage is despite hardly any big upsets on the first day of the tournament. No. 12 Murray State was the lowest-seeded team to win an opening game, and the Racers were one of the most popular upset picks.

Read more: Here are the most likely March Madness upsets, according to Las Vegas

Other than Murray State, just three teams — No. 10 Florida, No. 10 Minnesota, and No. 9 Baylor — defeated a team with a higher seed.

In other words, despite an extremely calm first day of action in terms of upsets, about one in every 400 brackets made it through without a loss.

With another full slate of games on Friday, that number is likely to dwindle even quicker as we head into the second round of the tournament.