The term J-curve is used in several different fields to refer to a variety of unrelated J-shaped diagrams where a curve initially falls, but then rises to higher than the starting point.

In private equity, the J curve is used to illustrate the historical tendency of private equity funds to deliver negative returns in early years and investment gains in the outlying years as the portfolios of companies mature.

In the early years of the fund, a number of factors contribute to negative returns including management fees, investment costs and under-performing investments that are identified early and written down. Over time the fund will begin to experience unrealized gains followed eventually by events in which gains are realized (e.g., IPOs, mergers and acquisitions, leveraged recapitalizations).

Historically, the J-Curve effect has been more pronounced in the US, where private equity firms tend to carry their investments at the lower of market value or investment cost and have been more aggressive in writing down investments than in writing up investments. As a result, the carrying value of any investment that is underperforming will be written down but the carrying value of investments that are performing well tend to be recognized only when there is some kind of event that forces the private equity firm to mark up the investment.

In mathematics, a curve (also called a curved line in older texts) is, generally speaking, an object similar to a line but which is not required to be straight. This entails that a line is a special case of curve, namely a curve with null curvature. Often curves in two-dimensional (plane curves) or three-dimensional (space curves) Euclidean space are of interest.

Various disciplines within mathematics have given the term different meanings depending on the area of study, so the precise meaning depends on context. However many of these meanings are special instances of the definition which follows. A curve is a topological space which is locally homeomorphic to a line. In every day language, this means that a curve is a set of points which, near each of its points, looks like a line, up to a deformation. A simple example of a curve is the parabola, shown to the right. A large number of other curves have been studied in multiple mathematical fields.

The term curve has several meanings in non-mathematical language as well. For example, it can be almost synonymous with mathematical function (as in learning curve), or graph of a function (as in Phillips curve).

Ian Bremmer (born November 12, 1969) is an American political scientist specializing in US foreign policy, states in transition, and global political risk. He is the president and founder of Eurasia Group, a leading global political risk research and consulting firm, and a professor at Columbia University. Eurasia Group provides financial, corporate, and government clients with information and insight on how political developments move markets. Bremmer is of Armenian and German descent.

Bremmer has authored/published eight books, including the national bestsellers Every Nation for Itself: Winners and Losers in a G-Zero World (Portfolio, May 2012), which details risks and opportunities in a world without global leadership, and The End of the Free Market: Who Wins the War Between States and Corporations (Portfolio, May 2010), which describes the global phenomenon of state capitalism and its implications for economics and politics. He also wrote The J Curve: A New Way to Understand Why Nations Rise and Fall (Simon & Schuster, 2006), selected by The Economist as one of the best books of 2006.