Why is Shakespeare more popular than ever?

It's amazing, don't you think? Shakespeare is more popular today than he has been at any point since his death four centuries ago (there are no hard-and-fast stats to actually prove it, but the scholars to whom I have spoken all agree it is the case).

The Internet has played its part in the brand Bard propagation (Spark Notes, hem, hem), but it has also produced a mountain of alternative, more contemporary content upon which we could choose to feast. And yet it is Shakespeare who has risen to the top. And not just online where he's looked up so much that there are now bespoke Shakespeare search engines.

You'll find him sitting on shelves in African bookshops, on laptops in Lapland, and on stage in jungle theatres. You'll hear his words pop up in pop songs, being quoted in movies, and spoken on the street.

Say: "To be or not to be" in just about any country and the locals will know that you're quoting Shakespeare. Crime novelists, business folk, football managers and lawyers all plunder his lexicon for that catchy title or perfectly apt phrase.

How did it happen? How has Shakespeare survived and thrived and transformed into an international superstar, when his contemporaries have not? Okay, fellow playwrights from the Elizabethan Golden Age of theatre are still knocking about - Marlowe, Jonson, Fletcher et al - but not in anything like the same omnipresent way.

What has Shakespeare's work got that theirs hasn't? In fact, what is it about his writing that outlasts and outwits just about every other wordsmith that's ever lived?

There is no writer on the planet who has as much work in daily play as that produced by the Sweet Swan of Avon (as Ben Jonson called him). Not even JK Rowling or Bob Dylan can better the Bard. The man and his words permeate the lives of billions of people.

Simon Russell Beale, the acclaimed Shakespearian actor, thinks it is the inherent adaptability of the plays that has made them such hearty and hardy travellers over time and space. "There are no rules with Shakespeare," he says. And then quotes the old joke in which the great director says to the young actor: "There are a thousand ways to play Hamlet [beat] and that's not one of them."

The point being, there are a thousand ways to play Hamlet. There are not a thousand ways to play Willy Loman, the delusional protagonist in Arthur Miller's play, Death of a Salesman. Nor, typically, with a Samuel Beckett part, where the playwright's handed-down directional wishes tend to be very specific. And, there's not a lot of wriggle room for an actress playing Ibsen's Hedda Gabler, or an actor taking on Chekhov's Konstantin in The Seagull.

It seems only Shakespeare was able to create highly believable three-dimensional characters that can morph in myriad ways. His characters are, Russell Beale says, "very hospitable" to actors.

The same applies to his plays, which Andrew Dickson, author of the recently published Worlds Elsewhere: Journeys Around Shakespeare's Globe, says have an "openness" that allows them to be endlessly reinterpreted.

They were "designed to be reinvented", says Dickson. Partly because they had so many different audiences to please when originally written - one afternoon Shakespeare would find his work being performed for the royal court, the following day the same piece would be played before the groundlings of Blackfriars.

But more importantly, they often started life elsewhere. Shakespeare's plays weren't always entirely his in the first place.

Professor Gordon McMullan, Director of the London Shakespeare Centre at King's College, London, says Shakespeare "was first and foremost an adapter" (Dickson describes the Bard as "a shameless hack"). He cites Romeo And Juliet as a centuries-old story Shakespeare took and rewrote. "I'm not saying he was a plagiarist, but he did rely heavily on pre-existing works."

Improvisation was Shakespeare's thing - lines and parts could be added or removed on a whim, variety was the spice of his writing life with multiple versions of the same play frequently on offer (there are at least three different Hamlet manuscripts).

He was not bound up in dogma. If he was struggling to find a suitable word or phrase to describe some action he would simply invent one (try doing that in your school Shakespeare essay). And if he wasn't sure how to end a scene or an act he wouldn't fret about it all night, but instead write a variety of alternatives and hand the problem over to his actors to solve.

It was he who set the precedent that his dramatic works were ripe for customisation. Go ahead, was his implicit invitation to all future writers, actors, and directors, pimp my plays - cut, paste, adapt, and reinterpret.

And so they have been, time and time again. Stephen Sondheim and Leonard Bernstein turned Romeo And Juliet into the musical West Side Story. The Bollywood director Vishal Bhardwaj transformed Macbeth into a gangster movie called Maqbool (2003).

And these are but two examples of thousands of re-imaginings of Shakespeare's plays that have occurred across the world. Which begs the question - why has he travelled so far, so successfully?

The familiar argument is that his poetic words travelled first-class on the imperial winds of Empire. As England and then Britain extended her reach across the globe, Shakespeare's plays became an important tool of indoctrination, and in Dickson's view, subjugation: "Shakespeare was imposed on Indian children to instil British culture and values." The colonial concept was "teach Shakespeare and they become like you".

According to Dickson: "You had to be able to quote Shakespeare at length to land a job in the Indian Civil Service - a test that was maintained right up until the 1920s."

But people and Shakespeare can't be tamed so easily. Dickson says the Indians quickly saw the merits in this English literary export. They liked his stories, and so rewrote them in their native language with the overbearing British often cast in highly unfavourable light.

Such revisions are made easy by the nature of the plays. Many of Shakespeare's stories are set in abstract places with plots that apply to many cultures - Hamlet is about revenge and a young man who doesn't get on with his step-father, Othello is ostensibly about jealousy and Twelfth Night is a good old farce based on mistaken identity. And it is this universal aspect of his work that ultimately makes it so timeless and timely.

The Rwandans see Hamlet as a story of revenge, while some contemporary Manhattan audiences draw a parallel with King Lear's sad decline with their own perceptions of America's diminishing powers. The Chinese are particularly keen on The Merchant Of Venice for reasons Dickson says date back to its war with Japan and a feeling of inferiority. The Germans - who have long considered Shakespeare to be theirs - found profound meaning in A Midsummer Night's Dream during the Cold War because of the first scene in Act V, in which a wall divides:

And thou, O wall, O sweet, O lovely wall,

That stand'st between her father's ground and mine!

Thou, O wall, O sweet and lovely wall,

Show me thy chink, to blink through with mine eyne!

Ultimately, though, it has to come down to the writing. I know when Shakespeare travels the texts get changed and much can be lost in translation, but the works are imbued with his brilliance.

Even if the words are not the same, the sense of meaning and rhythm remain. He was an extraordinarily gifted observer of the human condition who also happened to have the literary skills to put what he saw into words that resonated in Elizabethan England at first, and now across the globe.

Of course he wasn't faultless. His modern resurgence started with Coleridge and the Romantics who - like the Germans - were fond of the idea of the solitary genius. We shouldn't fall into the same rose-tinted trap. As Simon Russell Beale says, as a playwright "he could be terrible", but then, as the actor is quick to add, "at his best he is the very best".

Subscribe to the BBC News Magazine's email newsletter to get articles sent to your inbox.