{
  "title": "Why projects overrun: the planning fallacy",
  "url": "https://www.shr.swiss/blog/pourquoi-les-projets-depassent-leurs-delais-le-biais-de-planification-en",
  "language": "en",
  "datePublished": "2026-09-10",
  "publisher": {
    "name": "SHR — Swiss Human Resources",
    "url": "https://www.shr.swiss",
    "address": "Esplanade de Pont-Rouge 9A, 1212 Lancy, Suisse"
  },
  "summary": "Teams systematically underestimate how long their own tasks take. Research offers a simple corrective: the outside view.",
  "section": "Research",
  "topic": "Project Management",
  "place": {
    "name": "Zurich",
    "region": "Zurich",
    "country": "CH"
  },
  "keyPoints": [
    {
      "heading": "The measured phenomenon",
      "point": "Roger Buehler, Dale Griffin and Michael Ross (1994, Journal of Personality and Social Psychology) show people predict over-optimistic completion times for their own tasks, even while recalling past predictions were wrong."
    },
    {
      "heading": "Inside and outside view",
      "point": "Daniel Kahneman and Dan Lovallo (1993, Management Science) contrast the 'inside view', focused on the project's scenario, with the 'outside view', based on outcomes of comparable projects."
    },
    {
      "heading": "The collective nuance",
      "point": "In teams, social pressure and the wish to convince a sponsor may amplify optimism, though group research is thinner than individual research."
    },
    {
      "heading": "The limit of common practice",
      "point": "Adding a flat buffer at the end treats the symptom without questioning the estimate; the buffer is often consumed or negotiated away.."
    },
    {
      "heading": "A practical check in Zurich",
      "point": "Before fixing a deadline, find three comparable internal projects and their actual duration, then test the estimate against them."
    }
  ],
  "sources": [
    {
      "authors": "Ross",
      "year": "1994",
      "source": "Journal of Personality and Social Psychology"
    },
    {
      "authors": "Lovallo",
      "year": "1993",
      "source": "Management Science"
    }
  ],
  "wordCount": 186,
  "image": "https://www.shr.swiss/img/blog-editorial-2026-09-10-en.jpg?v=4",
  "translations": {
    "fr": "https://www.shr.swiss/blog/pourquoi-les-projets-depassent-leurs-delais-le-biais-de-planification",
    "en": "https://www.shr.swiss/blog/pourquoi-les-projets-depassent-leurs-delais-le-biais-de-planification-en",
    "de": "https://www.shr.swiss/blog/pourquoi-les-projets-depassent-leurs-delais-le-biais-de-planification-de",
    "it": "https://www.shr.swiss/blog/pourquoi-les-projets-depassent-leurs-delais-le-biais-de-planification-it"
  },
  "relatedPages": {
    "programme": "https://www.shr.swiss/formation/gestion-de-projet/zurich",
    "city": "https://www.shr.swiss/formations-ville/zurich",
    "blog": "https://www.shr.swiss/blog"
  },
  "citationPolicy": "Citation autorisée avec mention « SHR — Swiss Human Resources » et lien vers l'article."
}