The reason is usually given as the rise of tablets and smartphones, which have replaced the PC and laptop for casual use for most people. Now, analyst Horace Dediu, of Apple watching consultancy Asymco, has published a wonderful graph which really shows the story.

The graph, above, simply shows the quarterly rate of growth (and decline) in Windows PC shipments since the launch of the first iPad in 2010. Bi (before iPad), PC sales were growing at above 20% a quarter. Ai (after iPad) they dropped below 10%, and are now in decline.

And the rate of decline is increasing, Last quarter worldwide Windows PC shipments fell by 12%, in a market that had already seen four consecutive quarters of the oxymoronically titled ‘negative growth’.

This is as clear a picture as you need of what is happening to the PC market. Much of the growth in PC sales had to do with casual users, both at home and in business, using them to access the Internet, consume digital media, and perform light PC functions like composing sending emails.

Now they can do all that on a tablet, or smartphone. Just as Apple pioneered the smartphone market with the iPhone, it pioneered the tablet market with the iPad. It remains the premier brand in both markets, but its success has ushered in the proliferation of cheap Android devices with truly astonishing price-performance.

PCs will never die. Power users need their flexibility, and they are demonstrably better for many functions, particularly those involving computation or sophisticated content creation. But they will decline in importance, and in numbers.

Most people on earth now access the Internet through a non-PC device. The proportion will continue to rise, just as PC shipments will continue to fall. The 30 year reign of the personal computer has come to an end.