What we think of as "Christmas music" is really just a seasonal exercise in baby boomer nostalgia.

That, at least, is one takeaway from the list of the top 30 most-played Christmas songs of all time, compiled by the American Society of Composers, Authors and Publishers (ASCAP). Nearly two-thirds of these songs were written in the 40s and 50s -- when the baby boomers were small children.

No holiday songs from the 2000s or the present decade crack the top 30. The closest is Mariah Carey's 1994 hit "All I Want for Christmas is You." And only one 80s song makes it -- George Michael's risible "Last Christmas."

But that's far from the worst song on the list. That honor goes to the MIDI-synthesized abomination that is Paul McCartney's "Wonderful Christmastime," which I'm forcing myself to listen to as I write this.

Overwhelmingly, though, the sound of Christmas is trapped in the mid-20th century. Web comic artist Randall Munroe (of XKCD fame) made this observation back in 2009, when ASCAP released its original list of the 20 top Christmas songs of the 2000s: "Every year, American culture embarks on a massive project to carefully recreate the Christmas of Baby Boomers' childhoods," he wrote. Or, more concisely, "an 'American tradition' is anything that happened to a Baby Boomer twice."

Plenty of ink has been spilled on why it's so hard for new holiday songs to gain traction with listeners. Part of the reason the boomers' childhood classics endure is that the postwar era really was an exceptional time in American history: jobs were plentiful, the economy was booming, and America's influence on the world stage was at its peak.

What we now think of as the holiday aesthetic isn't just about a particular time of the year -- it's also very much about a particular time of American history. That golden postwar era casts a long shadow across the decades that have come after. Many contemporary policy discussions -- on big topics like inequality and political polarization -- are animated by a comparison between that period and the present one.

We still haven't fully figured out whether that postwar boom period represented a baseline that we can return to, or an anomaly reflecting a unique convergence of historic circumstances. So it shouldn't come as a surprise that during the most nostalgic time of the year, our music tastes remain stubbornly stuck in the past.