Individuals & Families

The market went up today. Does that tell you anything about tomorrow?

Take a handful of beads and drop them, one at a time, through a lattice of pegs arranged in a honeycomb pattern.

In 1846, a dataset appeared in the Edinburgh Medical and Surgical Journal that would change the history of statistics.

In the Prussian army in the late nineteenth century, soldiers were occasionally killed by horse kicks — rare, but across a large army over many years, it happened with a certain regularity.

In the last episode, Legendre gave science its most powerful practical tool for fitting models to noisy data. He showed how to find the line — the function — that minimizes the sum of squared errors. He proved it worked. But he did not fully explain why it was the right method rather than simply a convenient one.

It is 1801. In Palermo, Sicily. The astronomer Giuseppe Piazzi has spotted something new — a faint point of light moving against the stars.

By the end of the eighteenth century, probability theory had accumulated a remarkable collection of results.

Imagine you visit a doctor. She runs a test for a rare disease, one that affects one person in a thousand.

Here is a game. We flip a fair coin, repeatedly, until it lands tails. If tails appears on the first flip, you win two dollars.

It’s London, 1733. Picture one of the greatest mathematicians of his generation — a personal friend of Isaac Newton.

Flip a coin. Heads or tails? You know going in that the odds of heads is one in two.

You already know two things about Gottfried Wilhelm Leibniz, born in Germany in 1646 — even if you don't know you know them.

By 1655, word had spread through the mathematical circles of Paris that something remarkable had happened the previous summer.

If a game is interrupted halfway through, how do you fairly split the pot? Okay, we asked that in the last episode, but bear with me…

It’s the summer of 1654. Two mathematicians in France are exchanging letters about a gambling problem.

It's Florence, around 1620. The grand duke's courtiers are arguing — again — about dice

It's 1550, and a physician in Milan has a problem. He's brilliant — one of the most famous doctors in Europe. He's also broke.

It's the year 1200. You're a merchant in Pisa, one of the busiest ports in the Mediterranean.

It's 2010. The US economy is clawing back from the worst financial crisis since the Great Depression, the Affordable Care Act reshapes American healthcare, and Apple launches the iPad.

It's 1998. The Clinton impeachment proceedings grip Washington, the European Central Bank is established and eleven nations are selected to adopt the Euro as their single currency, and two Stanford PhD students launch a search engine called Google.

It's 1960. JFK is on the campaign trail, NASA launches America's first weather satellite, and ABC premieres The Flintstones — the first animated series created specifically for prime-time tv.

It's 1994. Nelson Mandela becomes South Africa's first democratically elected president. A former Wall Street trader named Jeff Bezos founds an online bookshop called Amazon. And Forrest Gump is packing theaters across America.

It's 1986. The Space Shuttle Challenger is lost, Halley's Comet returns for the first time in 76 years, and Top Gun is breaking box-office records across America.

It's 1964. The Vietnam War is Escalating. The Civil Rights Act becomes law. And Beatlemania is sweeping America. Meanwhile, Wall Street is booming.

It's 1969. Wall Street traders believe they can outsmart the market by reacting faster to news than anyone else.

You're running a pension fund. Thousands of retirees are counting on you to grow their savings. So you do what everyone does — you hire fund managers with the best recent track records.

It's 1976. An investor asks a simple question: How have stocks actually performed compared to bonds over the long term? Nobody knew.

It's 1965. Computers fill entire rooms. On Wall Street, armies of analysts pore over balance sheets, earnings reports, and economic data.

December 1990. William Sharpe receives the Nobel Prize in Economics at Stockholm City Hall.

Walk into any Wall Street brokerage in 1965, and you'll see the same thing: analysts hunched over charts, tracing patterns with their fingers.

It's the late 90's. The internet is transforming everything, including how Americans invest.

For nearly 30 years, finance had one answer to every question about risk: beta. Market exposure. That single number supposedly explained why some stocks delivered higher returns than others.

It's 1979. Finance has a comfortable certainty: investors are rational creatures who calculate risk, weigh probabilities, and choose whatever maximizes their utility.

In 1952, investing advice boiled down to one thing: pick winning stocks. Find the next big company, put your money in, hope it soars