{"id":1856,"date":"2019-06-15T17:35:00","date_gmt":"2019-06-15T17:35:00","guid":{"rendered":"https:\/\/analystprep.com\/cfa-level-1-exam\/?p=1856"},"modified":"2026-01-13T11:54:34","modified_gmt":"2026-01-13T11:54:34","slug":"forms-market-efficiency","status":"publish","type":"post","link":"https:\/\/analystprep.com\/cfa-level-1-exam\/equity\/forms-market-efficiency\/","title":{"rendered":"Weak, Semi-strong, and Strong Forms Market Efficiency"},"content":{"rendered":"\n<script type=\"application\/ld+json\">\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@type\": \"VideoObject\",\n\n  \"name\": \"Market Efficiency (2024\/2025 Level I CFA\u00ae Exam \u2013 Equity \u2013 Module 3)\",\n\n  \"description\": \"This video lesson covers market efficiency concepts, including market value vs. intrinsic value, factors influencing efficiency, forms of market efficiency (weak, semi-strong, strong), implications for investment strategies, market anomalies, and behavioral finance's role in explaining inefficiencies and deviations from rational investor behavior.\",\n\n  \"uploadDate\": \"2022-05-10T00:00:00+00:00\",\n\n  \"thumbnailUrl\": \"https:\/\/analystprep.com\/default-thumbnail.jpg\",\n\n  \"contentUrl\": \"https:\/\/youtu.be\/7Ub4Gt-0nMs\",\n\n  \"embedUrl\": \"https:\/\/www.youtube.com\/embed\/7Ub4Gt-0nMs\",\n\n  \"duration\": \"PT1H05M44S\",\n\n  \"publisher\": {\n    \"@type\": \"Organization\",\n    \"name\": \"AnalystPrep\",\n    \"logo\": {\n      \"@type\": \"ImageObject\",\n      \"url\": \"https:\/\/analystprep.com\/default-logo.jpg\",\n      \"width\": 600,\n      \"height\": 60\n    }\n  }\n}\n<\/script>\n\n<blockquote class=\"wp-embedded-content\" data-secret=\"xiHypIeqJf\"><a href=\"https:\/\/analystprep.com\/cfa-level-1-exam\/equity\/forms-market-efficiency\/\">Weak, Semi-strong, and Strong Forms Market Efficiency<\/a><\/blockquote><iframe loading=\"lazy\" class=\"wp-embedded-content\" sandbox=\"allow-scripts\" security=\"restricted\" style=\"position: absolute; visibility: hidden;\" title=\"&#8220;Weak, Semi-strong, and Strong Forms Market Efficiency&#8221; &#8212; AnalystPrep | CFA\u00ae Exam Study Notes\" src=\"https:\/\/analystprep.com\/cfa-level-1-exam\/equity\/forms-market-efficiency\/embed\/#?secret=wdZjdRhWyj#?secret=xiHypIeqJf\" data-secret=\"xiHypIeqJf\" width=\"600\" height=\"338\" frameborder=\"0\" marginwidth=\"0\" marginheight=\"0\" scrolling=\"no\"><\/iframe>\n\n<script type=\"application\/ld+json\">\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@type\": \"QAPage\",\n  \"mainEntity\": {\n    \"@type\": \"Question\",\n    \"name\": \"If a skilled fundamental financial analyst and an insider trader all earn the same long-run risk-adjusted returns, what form of market efficiency is likely to apply?\",\n    \"text\": \"If a skilled fundamental financial analyst and an insider trader all earn the same long-run risk-adjusted returns, what form of market efficiency is likely to apply?\",\n    \"answerCount\": 3,\n    \"acceptedAnswer\": {\n      \"@type\": \"Answer\",\n      \"text\": \"Strong form.\"\n    },\n    \"suggestedAnswer\": [\n      {\n        \"@type\": \"Answer\",\n        \"text\": \"Weak form.\"\n      },\n      {\n        \"@type\": \"Answer\",\n        \"text\": \"Semi-strong form.\"\n      }\n    ]\n  }\n}\n<\/script>\n\n\n\n<iframe loading=\"lazy\"\n  width=\"611\"\n  height=\"344\"\n  src=\"https:\/\/www.youtube.com\/embed\/7Ub4Gt-0nMs\"\n  title=\"YouTube video player\"\n  frameborder=\"0\"\n  allow=\"accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share\"\n  referrerpolicy=\"strict-origin-when-cross-origin\"\n  allowfullscreen>\n<\/iframe>\n\n\n\n\n\n<p>Eugene Fama developed a framework of market efficiency that laid out three forms of efficiency: weak, semi-strong, and strong. Each form is defined with respect to the available information that is reflected in prices. Investors trading on available information that is not priced into the market would earn abnormal returns, defined as excess risk-adjusted returns.<\/p>\n<h2><strong>Weak Form<\/strong><\/h2>\n<p>In the weak-form efficient market hypothesis, all historical prices of securities have already been reflected in the market prices of securities. In other words, technicians \u2013 those trading on analysis of historical trading information \u2013 should earn no abnormal returns. Research has shown that this is likely the case in developed markets, but less developed markets may still offer the opportunity to profit from technical analysis.<\/p>\n<h2><strong>Semi-strong Form<\/strong><\/h2>\n<p>In a semi-strong-form efficient market, prices reflect all publicly known and available information, including all historical price information. Under this assumption, analyzing any public financial disclosures made by a company to determine a stock\u2019s intrinsic value would be futile since every detail would be taken into account in the stock\u2019s market price. Similarly, an investor could not earn consistent abnormal returns by acting on surprise announcements since the market would quickly react to the new information.<\/p>\n<h2><strong>Strong Form<\/strong><\/h2>\n<p>In a strong-form efficient market, security prices fully reflect both public and private information. Therefore, insiders could not generate abnormal returns by trading on private information because it would already figure into market prices. However, researchers find that markets are generally not strong-form efficient as abnormal profits can be earned when nonpublic information is used.<\/p>\n<h2><strong>Summary<\/strong><\/h2>\n<p>In the following graph, we can clearly see that the weak form of market efficiency reflects only past market data. In contrast, the strong form reflects all past data, public market information, and insider information.<\/p>\n<h4><strong>Market Prices Reflect<\/strong><\/h4>\n<p>$$<br>\\begin{array}{cccc}<br>\\textbf{Forms of market efficiency} &amp; \\textbf{Past market data} &amp; \\textbf{Public information} &amp; \\textbf{Private information} \\\\<br>\\hline<br>\\text{Weak form} &amp; \\checkmark &amp; &amp; \\\\<br>\\text{Semi-strong form} &amp; \\checkmark &amp; \\checkmark &amp; \\\\<br>\\text{Strong form} &amp; \\checkmark &amp; \\checkmark &amp; \\checkmark \\\\<br>\\end{array}<br>$$<\/p>\n<blockquote>\n<h3><strong>Question<\/strong><\/h3>\n<p>If a skilled fundamental financial analyst and an insider trader all earn the same long-run risk-adjusted returns, what form of market efficiency is likely to apply?<\/p>\n<ol style=\"list-style-type: upper-alpha;\">\n<li>Weak form.<\/li>\n<li>Strong form.<\/li>\n<li>Semi-strong form.<\/li>\n<\/ol>\n<p><strong>Solution<\/strong><\/p>\n<p>The correct answer is <strong>B<\/strong>.<\/p>\n<p>In strong form market efficiency, all information, both public and private (including insider information), is fully reflected in stock prices. This implies that even insider traders cannot consistently achieve superior risk-adjusted returns. Since both the skilled fundamental financial analyst and the insider trader are earning the same long-run risk-adjusted returns, it suggests that no advantage can be gained from private or public information, which is characteristic of strong form efficiency.<\/p>\n<\/blockquote>\n","protected":false},"excerpt":{"rendered":"<p>Weak, Semi-strong, and Strong Forms Market Efficiency Eugene Fama developed a framework of market efficiency that laid out three forms of efficiency: weak, semi-strong, and strong. Each form is defined with respect to the available information that is reflected in&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[8],"tags":[],"class_list":["post-1856","post","type-post","status-publish","format-standard","hentry","category-equity","blog-post","no-post-thumbnail","animate"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.9 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Forms of Market Efficiency | CFA Level 1 - AnalystPrep<\/title>\n<meta name=\"description\" content=\"Market efficiency exists in three forms\u2014weak, semi-strong, and strong\u2014each reflecting different levels of information incorporation in asset prices\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/analystprep.com\/cfa-level-1-exam\/equity\/forms-market-efficiency\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Forms of Market Efficiency | CFA Level 1 - 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