Isabella Walker, autor en Straytrees

Nov

10

2026

The unexpected benefits of concentrated stock portfolios

Under mean-variance portfolio theory, the optimal level of diversification today exceeds 300 stocks. The average investor holds three or four. That distance is one of the best documented anomalies in finance, and its cost has been measured: households with below-median financial literacy who rely on their own judgement lose an expected 50 basis points a year on average. But there is an uncomfortable result worth knowing before closing the case: in one sample of brokerage accounts, households with concentrated portfolios outperformed diversified ones. This article goes through what has been measured.Summary: the seven findings that matterEach row names the study…

Nov

10

2026

By Isabella Walker

AI breast cancer screening trial reports 29% increase in cancer detection without false positives

Science and Technology

Of everything promised about artificial intelligence in medicine, one case has completed the full course: randomised trial, prespecified primary endpoint, published result. It is breast cancer screening, and the trial is called MASAI. With 105,934 women randomised within Sweden's national programme, AI-supported reading detected 29% more cancers than standard double reading, without increasing false positives, and cut reading workload by 44%. And in 2026 came the missing figure: interval cancers, the endpoint that actually measures whether a screening programme is safe. This article explains why this case counts and what sets it apart.The 30-second summary: the seven figures that matterEach…

Nov

10

2026

By Isabella Walker

How industrial megaprojects uproot communities and disrupt lives

Social Responsibility

Understanding Industrial Megaprojects and DisplacementIndustrial megaprojects—large-scale developments such as dams, mining complexes, oil pipelines, ports, highways, and special economic zones—are often promoted as engines of economic growth. Governments and corporations argue that they generate jobs, energy security, and infrastructure. Yet behind these promises lies a recurring reality: entire communities are uprooted, livelihoods are disrupted, and cultural identities are weakened or erased.The World Bank estimates that development projects have displaced millions of people over the past several decades. Independent researchers suggest the true number may be significantly higher, especially when informal settlements and Indigenous territories are considered. Displacement can be physical,…

Nov

09

2026

By Isabella Walker

Free museums: 62% more visits, the audience that already went, and the minimal fee that pushes out exactly the people it was meant to attract

Culture and Entertainment

In 2001 the United Kingdom abolished admission charges at its national museums, and in 2002 the department announced 62% more visits in seven months. It stands as one of the most successful cultural policy figures of recent decades, frequently referenced whenever free admission becomes a topic of discussion globally.What almost never accompanies that figure is the question a market researcher asked himself the moment he read it, and which turned out to be the decisive one: were a lot more people visiting museums, or were the same people visiting more often? The survey he ran to find out showed that,…