You know it's Christmas if groups of strangers knock on your door uninvited and begin singing. National Go Caroling Day is Dec. 20, and the holiday gives everyone a reason to spread some holiday cheer by singing Christmas carols to anyone with a doorbell. All you have to do is get a group of friends, pick some of your best Christmas songs and serenade the neighborhood.
With so many to choose from, it's impossible to single out the best Christmas song, but for generations, entertainers have readied their voices in an effort to land a Christmas hit single that becomes the season's big holiday song. As Billboard points out, it is difficult to track the sales of holiday songs because there have been many changes in how music is released and tracked over the decades, but we've given it a try anyway.
In honor of National Go Caroling Day 2016, here are the top-selling Christmas songs of all time.
15. 'The Christmas Song' by Nat King Cole
Nat King Cole's "The Christmas Song" first broke the Hot 100 charts when it was released in 1960. After 1962, it fell off the charts for more than half a century before before breaking the top 100 once again in 2013 and the top 40 in 2015.
The beloved holiday classic reached No. 35 on the Streaming Songs charts with 5.4 million streams in 2015. It also broke through on the Holiday 100 chart and the Radio Songs chart.
Although that's not the same as sales, and sales information is elusive for the record, the song makes this list for its longevity and continued popularity.
14. 'Santa Baby' by Eartha Kitt
Bucking the trend of sentimental or child-focused Christmas songs, "Santa Baby" is the ballad of a woman with fine taste who expects Santa Claus to reward her good behavior with expensive things.
Born in 1927, Eartha Kitt's mother sent her from the cotton fields of her South Carolina home to live with family in Harlem when she was just eight years old. She went on to join an exclusive club of performers who were nominated for a Grammy, a Tony and an Emmy. She received multiple nominations of each.
"Santa Baby" has been covered extensively, most notably by Madonna, whose version has more than 2.8 million views on YouTube. Kitt died on Christmas Day in 2008.
Related: The 13 Richest Movie Santas of All Time
13. 'Last Christmas' by Wham
1980s British pop duo sensation Wham! — consisting of George Michael and Andrew Ridgeley — released "Last Christmas" in 1984. Since then, it has been downloaded more than 751,000 times.
The song has been covered by many artists, most notably Taylor Swift. Her version, released in 2012, has been viewed more than 3.4 million times on YouTube.
George Michael used Wham! as a springboard to fame, fortune and a wildly successful solo career that earned him a net worth of $200 million. Andrew Ridgeley, on the other hand, released one poorly received solo album, career hopped for a few decades and now lives in an English farmhouse, surfs and lives off Wham! royalties.
12. 'Jingle Bell Rock' by Bobby Helms
When it was released in 1957, "Jingle Bell Rock" was — and would forever remain — the biggest hit Bobby Helms ever released. The twangy holiday classic has been downloaded more than 780,000 times.
Country guitar icon Hank Garland played the song's familiar opening chords. The song has been covered by everyone from Hall & Oates and Brenda Lee to Straight No Chaser and The Muppets.
11. 'Feliz Navidad' by Jose Feliciano
While some Christmas songs fade away after a few years, crossover classic "Feliz Navidad" continues to gain popularity every season. Even Puerto Rico native Jose Feliciano continues to be surprised by his song's success and longevity.
"Feliz Navidad" is in the Grammy Hall of Fame. To date, the bilingual classic has been downloaded more than 808,000 times since it was released in 1970.
One of the most familiar holiday songs ever written, "Feliz Navidad" has been covered by everyone from Celine Dion to the Three Tenors. It has also appeared in countless commercials. Feliciano has a net worth of $12 million.
10. 'Where Are You, Christmas?' by Faith Hill
Country superstar Faith Hill lays claim to one of the most popular Christmas songs ever written. "Where are You, Christmas?" has been downloaded more than 897,000 times.
The 2000 song was a breakout hit on the soundtrack of the blockbuster holiday movie "How the Grinch Stole Christmas" of the same year. Mariah Carey is credited as one of the song's writers.
One of the biggest stars in country music, Faith Hill has won a Grammy and was nominated for four others. She has a net worth of $80 million.
9. 'Christmas Canon' by Trans-Siberian Orchestra
The Trans-Siberian Orchestra reinvented Pachelbel's "Canon in D Major" with the hard-rock "Christmas Canon." The 1990s holiday hit has been downloaded more than 918,000 to date.
The genre-busting group is still a major road act. They've sold more than $280 million worth of tickets in the last decade.
The group has also sold more than 10 million albums. Keeping with the Christmas spirit, the Trans-Siberian Orchestra has donated more than $11 million to charity.
8. 'Rockin' Around the Christmas Tree' by Brenda Lee
Brenda Lee released "Rockin' Around the Christmas Tree" in 1958 when she was just 13 years old. The song didn't become a hit, however, until 1960, after Lee scored a few other big singles.
Holiday hit machine Johnny Marks wrote the song, which has been downloaded at least a million times. It has been recorded by the likes of Alabama, LeAnn Rimes, Toby Keith and Miley Cyrus.
According to Country Music Television, Brenda Lee was as important to country music's crossover into the mainstream as Patsy Cline. Lee has a net worth of $20 million.
7. 'Mistletoe' by Justin Bieber
Pop superstar Justin Bieber made Beliebers out of holiday music aficionados everywhere with "Mistletoe." Released in 2011, the acoustic pop track has scored more than 1.1 million downloads.
The Biebs continues to be a pop music force. His songs have earned nearly 11.5 billion views on YouTube and he once sold out Madison Square Garden in 22 minutes.
In total, he's sold 15.25 million albums and more than 318 million concert tickets. Bieber has an estimated net worth of $225 million.
6. 'Christmas Eve (Sarajevo 12/24)' by Trans-Siberian Orchestra
The Trans-Siberian Orchestra strikes twice on this list, this time with "Christmas Eve (Sarajevo 12/24)." According to Billboard, the 90s Christmas hit racked up 1.3 million downloads to date.
In 2003, Trans-Siberian Orchestra's Paul O'Neill told "Christianity Today" that the now classic Christmas song is based on the life of a brilliant cellist born in Sarajevo. When the musician returned home to find his country in ruins from the Bosnian War, he played his cello in the ruins instead of hiding from the bombings.
The Trans-Siberian Orchestra is one of the biggest touring acts of the last two decades. They've performed in more than 80 cities to more than 100 million people.
5. 'Do You Want to Build a Snowman?' by Kristen Bell
More than 1.6 million people have downloaded "Do You Want to Build a Snowman?" by Kristen Bell. Agatha Lee Monn and Katie Lopez also appear in the song, which was released in 2013.
Part of the song's success can be attributed to its appearance on the soundtrack for Disney's widely popular animated movie, "Frozen." According to Billboard, the song almost didn't make the cut for the film because it was so sad.
Kristen Bell, who played the voice of Anna in "Frozen," has a net worth of $20 million. A multi-talented entertainer, she has nearly 80 acting credits.
4. 'All I Want For Christmas Is You' by Mariah Carey
The No. 4 Christmas hit single of all time belongs to Mariah Carey. "All I Want for Christmas is You" was released in 1994 and, according to Billboard, continues to get more popular every year.
To date, the song has been downloaded more than 3.2 million times. That's twice as many purchases than the next best-selling Christmas single.
The song peaked at No. 2 and stayed on the charts for a staggering 75 weeks. The best-selling female performer of the 1990s, Mariah Carey counts "All I Want for Christmas is You" as just one feather in her cap. The superstar's long, illustrious career has earned her a net worth of $520 million.
3. 'Do They Know It's Christmas?' by Band Aid
On Nov. 25, 1984, some of the biggest artists in the music world were all in the same place at the same time to record a single song. Band Aid was made up of predominantly English superstars like Bono, Duran Duran, Boy George, George Michael and Sting.
The dark and morbid "Do They Know it's Christmas" served as a reminder that the greed and excess of 1980s America didn't apply to much of the world. The producer was inspired to form the collaboration after seeing graphic images of famine in Ethiopia.
"Do They Know it's Christmas?" sold 3.79 million copies and the song raised at least $24 million for charity. In 2014, a second Band Aid all-star group was organized to raise money to fight ebola.
2. 'Rudolph, the Red-Nosed Reindeer' by Gene Autry
Singing cowboy Gene Autry recorded "Rudolph, the Red-Nosed Reindeer" on June 27, 1949. It has since sold more than 12 million copies, making it the No. 1 best-selling single in the history of Columbia Records.
In the ensuing years, "Rudolph, the Red-Nosed Reindeer" has been recorded more than 500 times by other artists. In 1985, it was inducted into the Grammy Hall of Fame.
The song has sold more than 8 million copies of sheet music and 25 million copies for orchestras and bands in 140 different arrangements.
1. 'White Christmas' by Bing Crosby
The No. 1 Christmas hit single of all time belongs to Bing Crosby. According to Guinness World Records, "White Christmas" is not just the biggest holiday song ever recorded, but the best-selling single ever in any genre — by a mile.
Irving Berlin wrote "White Christmas" in 1940, and the song was recorded in 18 minutes in the spring of 1942. To date, it has sold 50 million copies — 17 million more than the next closest single, "Candle in the Wind" by Elton John.
The classic carol spent 11 weeks at No. 1 on that era's version of the Billboard Hot 100 chart. Crosby had a net worth of $50 million adjusted for inflation when he passed away in 1977.
Up Next: 6 Reasons to Skip Christmas and Travel Instead
You can use National Happy Go Caroling Day as an opportunity to belt out some of your favorite Christmas classics. But when the pros do it, some of those classics rise to join the ranks of history's most successful records.
This article originally appeared on GOBankingRates.com: Happy Go Caroling Day: 15 of the Best Selling Christmas Songs of All Time