If Data Was Stored on Punch Cards, How Much Space Would Google Need?

Imagine if all the world's data was still stored on punch cards: we'd be drowning in cardboard. But just how much exactly?

Fortunately, XKCD's Randall Munroe has taken a stab at working that out. He explains, based on the assumption that Google has a storage capacity of 15 exabytes:

Let's assume Google has a storage capacity of 15 exabytes, or 15,000,000,000,000,000,000 bytes. A punch card can hold about 80 characters, and a box of cards holds 2000 cards. 15 exabytes of punch cards would be enough to cover my home region, New England, to a depth of about 4.5 kilometers. That's three times deeper than the ice sheets that covered the region during the last advance of the glaciers.

If Data Was Stored on Punch Cards, How Much Space Would Google Need?

That's quite a lot of card. Thank goodness we went digital. [What If?]