Workplace culture through the 20th century worked on something of a Pavlov's dog principle: Ring the right bells at regular intervals and your employees would sit up and be good for you.

In the 21st century, great work cultures require thought, personalization, and innovation. A good reason for this is that employers are no longer dealing with loyal, career employees of generations past. On the one hand, we have the gig economy; on the other, a highly fluid workforce of recent graduates (aged 25-34) spending an average of just 2.8 years in their jobs.

Employers that want the best talent need to get creative with what they offer if they want to attract strong applicants and retain the hotshots they already have.

These were not your parents' perks

The world's most successful companies are leading the way. Google and Apple are renowned for the perks and culture new employees can expect. Sure, they have lots of money to pump into schemes like celebrity speakers and on-site massage therapy, but it is telling that they choose to spend money this way rather than pump it all into (even) higher salaries. 

Google even facilitates its employees' work-work balance. The company used to encourage staff to spend up to one-fifth of their time developing their own ideas. And as well as offering financial support for employees to take courses and tuition, Google makes it easier for them to pursue their dreams by taking care of things like free and healthy lunches, on-site workout classes, and transportation to and from work.

Apple's workers get significant discounts on the company's product, which has the added advantage of creating a real army (don't call it a cult!) of Apple advocates. And not only does the company offer reasonable levels of maternity and paternity leave (still a rarity in the U.S.), but it offers the (controversial) option of freezing your eggs.

Company parties feature performances from leading musicians and pop stars, and -- this one's the headline-grabber -- free beer.

The message from apparently monolithic companies such as these is that work should be part of life, not just something you do to fund your life. Whether such a sentiment is heartfelt or just canny PR is impossible to say, but the result is the same: Everyone wants to work at Apple or Google.

However, these are only the headline companies. A lot of other hugely successful businesses are thriving because their staff is talented and they love working for them. For an idea on who some of these businesses are -- and where to continue your research as you draft your new HR strategy -- check out these new visualizations which illustrate the world's best companies to work for. They must be doing something right!