Misc
Calculating the Lifetime Value of a Customer
Calculating the Lifetime Value of a Customer
What is one customer worth to a business, and what should a business be willing to pay to acquire the said customer?
It all comes down to a concept called “customer lifetime value”, which is used to describe the approximate value of one customer to a business. It is essentially the average amount of money made over the lifespan of an average customer, discounted by future cash flows.
The higher the value, the higher the marketing budget can be to acquire each customer. This is not only a key concept to understand in business, but also for investors that are looking to put money in consumer-oriented companies.
Original graphic by: KISSmetrics
Maps
The Incredible Historical Map That Changed Cartography
Check out the Fra Mauro Mappa Mundi (c. 1450s), a historical map that formed a bridge between medieval and renaissance worldviews.

The Incredible Historical Map That Changed Cartography
This map is the latest in our Vintage Viz series, which presents historical visualizations along with the context needed to understand them.
In a one-paragraph story called On Exactitude in Science (Del Rigor en la Ciencia), Jorge Luis Borges imagined an empire where cartography had reached such an exact science that only a map on the same scale of the empire would suffice.
The Fra Mauro Mappa Mundi (c. 1450s), named for the lay Camaldolite monk and cartographer whose Venetian workshop created it, is not nearly as large, at a paltry 77 inches in diameter (196 cm). But its impact and significance as a bridge between Middle Age and Renaissance thought certainly rivaled Borges’ imagined map.
One of ‘the Wonders of Venice’
Venice was the undisputed commercial power in the Mediterranean, whose trade routes connected east and west, stretching to Flanders, London, Algeria, and beyond.
This network was protected by fleets of warships built at the famous Arsenale di Venezia, the largest production facility in the West, whose workforce of thousands of arsenalotti built ships on an assembly line, centuries before Henry Ford.
The lion of St Mark guards the land gate to the Arsenale di Venezia, except instead of the usual open bible in its hands offering peace, this book is closed, reflecting its martial purpose. Source: Wikipedia
The Mappa Mundi (literally “map of the world”) was considered one of the wonders of Venice with a reputation that reached the Holy Land. It is a circular planisphere drawn on four sheets of parchment, mounted onto three poplar panels and reinforced by vertical battens.
The map is painted in rich reds, golds, and blues; this last pigment was obtained from rare lapis lazuli, imported from mines in Afghanistan. At its corners are four spheres showing the celestial and sublunar worlds, the four elements (earth, air, fire, and water), and an illumination of the Garden of Eden by Leonardo Bellini (active 1443-1490).
Japan (on the left edge, called the Isola de Cimpagu) appears here for the first time in a Western map. And contradicting Ptolemaic tradition, it also shows that it was possible to circumnavigate Africa, presaging the first European journey around the Cape of Good Hope by the Portuguese explorer Bartolomeu Dias in 1488.
NASA called the historical map “stunning” in its accuracy.
A Historical Map Between Two Worlds
Medieval maps, like the Hereford Mappa Mundi (c. 1300), were usually oriented with east at the top, because that’s where the Garden of Eden was thought to be. Fra Mauro, however, chose to orient his to the south, perhaps following Muslim geographers such as Muhammad ibn Muhammad al-Idrisi.
Significantly, the Garden of Eden is placed outside of geographic space and Jerusalem is no longer at the center, though it is still marked by a windrose. The nearly 3,000 place names and descriptions are written in the Venetian vernacular, rather than Latin.
At the same time, as much as Fra Mauro’s map is a departure from the past, it also retains traces of a medieval Christian worldview. For example, included on the map are the Kingdom of the Magi, the Kingdom of Prester John, and the Tomb of Adam.
Isidore of Seville, Etymologiae (c. 600–625). Source: Wikipedia
The circular planisphere also follows the medieval T-O schema, first described by Isidore of Seville, with Asia occupying the top half of the circle, and Europe and Africa each occupying the bottom two quarters (Fra Mauro turns the ‘T’ on its side, to reflect a southern orientation). Around the circle, are many islands, beyond which is the “dark sea” where only shipwreck and misfortune await.
Fra Mauro’s Legacy
Fra Mauro died some time before 20 October 1459, and unfortunately his contributions fell into obscurity soon thereafter; until 1748, it was believed that the Mappa Mundi was a copy of a lost map by Marco Polo.
In 1811, the original was moved from Fra Mauro’s monastery of San Michele to the Biblioteca Nazionale Marciana, following the suppression of religious orders in the Napoleonic era, where it can be viewed today.
Two digital editions have also been produced by the Museo Galileo and the Engineering Historical Memory project, where readers can get a glimpse into a fascinating piece of cartographic history.
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