Khipha ukugxekwa okubhekene nombono wesikhwama samanje kusuka kulesi sixhumanisi https://en.wikipedia.org/wiki/Modern_portfolio_theory, ubeke ohlwini lwezinhlamvu
Context:Naphezu kokubaluleka kwayo ngokomqondo, abagxeki be-MPT bayazibuza ukuthi ingabe iyithuluzi lokutshala imali elifanele yini, ngoba imodeli yayo yezimakethe zezimali ayihambisani nezwe langempela ngezindlela eziningi  Izinyathelo zengozi, ukubuya, kanye nokuhlobana okusetshenziswe yi-MPT kusekelwe [kulindeleke amanani] ((https://en.wikipedia.org/wiki/Expected_value), okusho ukuthi ziyizitatimende zezibalo mayelana nekusasa (inani elilindelekile lokubuya licacile kulezi zilinganiso ezingenhla, futhi lisho ngokucacile izincazelo ze [ukuphambuka] ((https://en.wikipedia.org/wiki/Variance) futhi [covariance] ((https://en.wikipedia.org/wiki/Covariance)). Izilinganiso ezinjalo ngokuvamile azikwazi ukubamba izici zezibalo zangempela zengozi kanye nokubuya okuvame ukulandela ukusatshalaliswa okuxekethile kakhulu (isb. [log-normal distribution] ((https://en.wikipedia.org/wiki/Log-normal_distribution)) futhi kungaholela, ngaphandle kokunciphisa [volatility] ((https://en.wikipedia.org/wiki/Volatility_(finance)), futhi ukukhula okuqhakazile kokubuya. Ngokuvamile lamazinga alindelekile awacabangi ngezimo ezintsha ezazingekho ngesikhathi kudalwa idatha yomlando.  Okubaluleke kakhulu, abatshalizimali banamathele ekulinganiseni amapharamitha abalulekile kusuka kudatha yemakethe yangaphambilini ngoba i-MPT izama ukumodela ubungozi ngokwezinga lokulahlekelwa, kodwa ayisho lutho ngokuthi kungani lezo zingozi zingenzeka. Izilinganiso zengozi ezisetshenzisiwe [i-probabilistic] ((https://en.wikipedia.org/wiki/Probability) ngokwemvelo, hhayi ngokwakhiwa. Lena umehluko omkhulu uma kuqhathaniswa eziningi izindlela zobunjiniyela ukuze [ukuphathwa kwezinhlekelele] ((https://en.wikipedia.org/wiki/Risk_management).  Ukulinganiswa kwengozi ngokwezibalo nakho kuyasiza kuphela uma kukhombisa ukukhathazeka kwangempela kwabatshalizimali - asikho isizathu sokunciphisa okuguquguqukayo okungekho muntu onendaba nakho empeleni. Ikakhulukazi, [ukuphambuka] (https://en.wikipedia.org/wiki/Variance) isilinganiso sokulingana esibala ukubuya okuphezulu okungajwayelekile njengengozi njengokubuya okuphansi okungajwayelekile. Isimo sengqondo [ukulahlekelwa ukugwema] ((https://en.wikipedia.org/wiki/Loss_aversion) umqondo wokuthi abatshalizimali bakhathazeke kakhulu ngokulahlekelwa kunokuzuza, okusho ukuthi umqondo wethu wokuqonda ingozi ngokuyisisekelo awalingani ngokwemvelo. Kukhona ezinye izilinganiso eziningi zengozi (njenge [izilinganiso zengozi ezihambisanayo] ((https://en.wikipedia.org/wiki/Coherent_risk_measure)) ezingase zibonise kangcono izintandokazi zangempela zabatshalizimali.  I-portfolio theory yanamuhla nayo iye yagxekwa ngoba icabanga ukuthi ukubuya kulandela [i-Gaussian distribution] (https://en.wikipedia.org/wiki/Normal_distribution). Kakade ngawo-1960, [Benoit Mandelbrot] kanye [Eugene Fama] babonisa ukungafaneleki kwalokhu kucatshangwa futhi basikisela ukusetshenziswa okujwayelekile [ukusabalalisa okuzinzile] esikhundleni salokho. [Stefan Mittnik] kanye [Slozar Rachev] wethule amasu okuthola amaphothifoliyo afanelekile kuzilungiselelo ezinjalo.  [abatshalizimali abaphikisayo] (https://en.wikipedia.org/wiki/Contrarian_investing) kanye [abatshalizimali be-value] (https://en.wikipedia.org/wiki/Value_investing) ngokuvamile ababhalisele i-Modern Portfolio Theory. Okunye ukuphikisa ukuthi i-MPT incike ku- [efficient-market hypothesis] (https://en.wikipedia.org/wiki/Efficient-market_hypothesis) futhi isebenzisa ukuguquguquka kwamanani amasheya njengendawo yengozi. i-MPT, futhi waphetha (njengoba kuchazwe ngumlobi wezindaba zokuphila): "umqondo wokuthi ukwakha amaphothifoliyo ngesisekelo sezibalo ezingathembekile nezingabalulekile, njengokuguquguquka komlando, walahlwa ukwehluleka.
- Izinyathelo zengozi, ukubuya, kanye nokuhlobana okusetshenziswe yi-Modern portfolio theory (MPT) kusekelwe kumanani alindelekile, lawo manani alindelekile ahluleka ukucabangela izimo ezintsha ezazingekho lapho kudalwa idatha yomlando - Ukulinganiswa kwengozi okusetshenziswe ku-MPT kungokungenzeka ngoba amamodeli e-MPT abeka ingozi ngokwezinga lokulahlekelwa okusekelwe kwimininingwane yangaphambilini yemakethe hhayi ukuthi kungani ukulahleka kwenzeka. - I-MPT izama ukunciphisa izingozi ngendlela yokwehluka. Kodwa-ke, le metric ayikhombisi ukukhathazeka kwangempela kwabatshalizimali. Ukwehluka kuyalingana, ngakho kujezisa ukubuya okuphezulu ngendlela efanayo nokulahlekelwa okukhulu. Nokho, abatshalizimali bakhathalela kakhulu ukulahlekelwa kunokuzuza, ngakho-ke umbono wengozi awalingani ngokwemvelo. Izilinganiso zengozi ezihambisanayo kufanele zibe imethrikhi engcono ekhombisa izintandokazi zabatshalizimali - I-MPT icabanga ukuthi izimbuyiselo zilandela ukusatshalaliswa kukaGaussian. Nokho, izazi eziningi zisikisela ukuthi ukubuya kungase kulandele ezinye ukusatshalaliswa ezifana ukusatshalaliswa esitebeleni - I-MPT isuselwa emcabangweni wemakethe esebenza kahle futhi iqala ngokuthi ukuguquguquka kwentengo yamasheya kuyindlela yokulinganisa ubungozi. Kodwa-ke, ukwakha iphothifoliyo ngokususelwa ekuguquguqukeni komlando kuyisisekelo esingabazekayo esigxekwe nguSir John Templeton