WASHINGTON — Futures contracts, one of the earliest forms of a derivative, have long been associated with big market failures. Harry Truman’s father was financially wiped out by agriculture futures, and rampant manipulation by speculators contributed to the market collapses of 1929. Regulators have long known that new trading instruments have a way of giving reassurance of stability in good times and of exacerbating market downturns in bad.

Futures — essentially, a promise to deliver cash or something of value at a later time — are traded on regulated exchanges such as the Chicago Mercantile Exchange, regulated by the Commodity Futures Trading Commission (CFTC). But Brooksley Born, chief of the CFTC, was not questioning bets on pork bellies or wheat prices, the bedrock of futures trading in simpler times. Her focus was the arcane class of derivatives linked to fluctuations in currency and interest rates. She told a group of business lawyers in 1998 that the “lack of basic information” allowed traders in derivatives “to take positions that may threaten our regulated markets or, indeed, our economy, without the knowledge of any federal regulatory authority.”

The future that Born envisioned turned out to be even riskier than she imagined. The real estate boom and easy credit of the past decade gave birth to more complex securities and derivatives, this time linked to the inflated value of millions of homes bought by Americans ultimately unable to afford them. That created a new chain of risk, starting with the heavily indebted homebuyers and ending in a vast, unregulated web of contracts worldwide.

By appearing to provide a safety net, derivatives had the unintended effect of encouraging more risk-taking. Investors loaded up on the mortgage-based investments, then bought “credit-default swaps” to protect themselves against losses rather than putting aside large cash reserves. If the mortgages went belly up, the investors had a cushion; the sellers of the swaps, who collected substantial fees for sharing in the investors’ risk, were betting that the mortgages would stay healthy.

The global derivatives market topped $530 trillion as of June 30 this year, including $55 trillion in the suddenly popular credit-default swaps; that $530 trillion represents all contracts outstanding. The total dollars at risk is much smaller, but still a hefty $2.7 trillion, according to an estimate by the International Swaps and Derivatives Association.

To make sense of those figures, compare them to the value of the New York Stock Exchange: $30 trillion at the end of 2007, before the recent crash. When the housing bubble burst and mortgages went south, the consequences seeped through the entire web. Some of those holding credit swaps wanted their money; some who owed didn’t have enough money in reserve to pay.

Instead of dispersing risk, derivatives had amplified it.