Most economists defer to the National Bureau of Economic Research (NBER) to officially determine the beginning and end of U.S. recessions. The NBER defines a recession as "a significant decline in economic activity spread across the economy, lasting more than a few months, normally visible in real GDP, real income, employment, industrial production, and wholesale-retail sales.” According to this definition, the economy is in recession when economic activity is declining. The recession ends when the decline ends—that is, when the economy begins to grow.
But after a decline in economic activity, resources are typically under-utilized, and unemployment is high. The economy may not be deteriorating, yet its performance remains disappointing. Most people would perceive the economy as weak and may think of it as still “in recession,” even though it’s technically no longer declining. To use an analogy from health: when the recession ends, the economy may not be getting any sicker, but it is still sick.
The Great Recession and its aftermath provide an important example of the difference between the technical definition of recession and the more common way that journalists and the general public use the term recession. The period of declining economic activity officially spanned eighteen months according to the NBER: from December 2007 to June 2009, after which the economy began to grow slowly. The technical “recession” ended by the summer of 2009. However, with disappointing growth, unemployment remained extraordinarily high. Additionally, the recovery has been so anemic that even four years after the technical recession ended, the economy still seems stagnant.
Therefore, people often think of the economy as “in recession” when economic activity, particularly the labor market, is weak—even if the economy is no longer declining.