Question: Who wrote an investment guide published by Orion in 1992 who named his approach to investment when he observed that after reading a short article on the Zulu people in the an American general-interest family magazine, published ten times a year his wife was better informed on the subject than he himself was ?

Context paragraphs:
Muskoka Magazine: Muskoka Magazine was a large format lifestyle magazine published ten times per year in Bracebridge, Ontario.  The magazine was freely delivered throughout the Muskoka region and in the greater Toronto area.  It existed between 2000 and 2016.

Valitut Palat: Valitut Palat is a Finnish language monthly general-interest family magazine published in Helsinki, Finland.  It is the Finnish edition of "Reader's Digest".

Wanderlust (magazine): Wanderlust is a British travel magazine, covering adventurous, cultural and special interest travel.  It is published ten times a year.  It was established in Windsor, Berkshire in 1993 by Paul Morrison and Lyn Hughes, who had observed the absence of a publication combining their interests in wildlife, activities and cultural insights.  Morrison died in December 2004 and Hughes took on the roles of publisher, managing director and editor-in-chief.  In 2008, the Haymarket Media Group bought a stake in the business.

Cosmogirl: CosmoGirl was an American magazine based in New York City, published from 1999 until 2008.  The teenage spin-off of "Cosmopolitan" magazine, it targeted teenage girls and featured fashion and celebrities.  It was published ten times a year and reached approximately eight million readers before folding.  The last issue was December 2008.  Subscribers instead received issues of fellow Hearst publication, "Seventeen".

Materials &amp; Design: Materials & Design is a peer-reviewed scientific journal published ten times per year by Elsevier.  The focus is researching practical applications of engineering materials including materials processing.  Article formats are regular articles, Express articles, and Review articles (typically commissioned by the Editors).  The Editor-in-Chief is Alexander Korsunsky (Trinity College, University of Oxford).

The Only Investment Guide You'll Ever Need: The Only Investment Guide You'll Ever Need is a book written by Andrew Tobias and concerns commonsense rules that the ordinary saver can live by.  Published in 1978 and revised every few years since then, it predated other popular investment books like the "Beardstown Ladies Investment Guide" and "Beating the Street" by Peter Lynch of Fidelity's Magellan Fund.  Along with Burton Malkiel's book "A Random Walk Down Wall Street" it helps ordinary readers see through the flim flam of investment marketing as well as being a sensible guide to personal finance.

Reader's Digest: Reader's Digest is an American general-interest family magazine, published ten times a year.  Formerly based in Chappaqua, New York, it is now headquartered in Midtown Manhattan.  The magazine was founded in 1920, by DeWitt Wallace and Lila Bell Wallace.  For many years, "Reader's Digest" was the best-selling consumer magazine in the United States; it lost the distinction in 2009 to "Better Homes and Gardens".  According to Mediamark Research (2006), "Reader's Digest" reaches more readers with household incomes of $100,000+ than "Fortune", "The Wall Street Journal", "Business Week", and "Inc." combined.

Five (magazine): Five is a German language basketball magazine, which was first published in August 2003.  It is subtitled, Basketball for Life! .  The founders were André Voigt and Jan Hieronimi.  André Voigt is also the editor-in-chief of "Five".  The magazine is published ten times a year by Park and Ride Sports GMBH and is based in Munich.  Its former headquarters was in Cologne.  It reports news about NBA through its permanent staff in Portland.  From 2007 the magazine has published a supplement, "Fünf", which features articles about the German Basketball Bundesliga.

The Zulu Principle: The Zulu Principle: Making Extraordinary Profits from Ordinary Shares is an investment guide written by English accountant and investor Jim Slater, first published by Orion in 1992.  Slater named his approach to investment when he observed that after reading a short article on the Zulu people in the "Reader's Digest" his wife was better informed on the subject than he himself was.  He went on to consider that if his wife read all the books she could find on the subject of Zulus, coupled with a visit to South Africa to meet them for herself, then in a relatively short period of time she could become one of the leading authorities on that "clearly defined and narrow area of knowledge".

Emperor Shaka the Great: Emperor Shaka the Great is an epic poem based on the Zulu oral tradition, compiled in Zulu then translated by South African Poet Mazisi Kunene.  The epic follows the life of Shaka Zulu.  The poem documents his exploits as a king of the Zulu people, produced considerable advances in State structure and military technologies of the Zulu.  Some critics express concern over the historicity of the retelling.  However, Kunene's embrasure of an African perspective on Shaka's Rule expresses an attempt at understanding the apparent horrors observed by Europeans in the Shaka's history.

Supporting paragraphs: The Zulu Principle Reader's Digest
Answer: Jim Slater