As of late 2018, the US expansion is nine years old and central banks have bought $15-16 trillion of assets.

There are two parts, judged as of November 2018. (1) The US expansion began in June 2009 (NBER trough), so it was about 9.4 years old in November 2018. 'Nine years' is correct if the trough date is roughly mid-2009. (2) Cumulative asset purchases by the major central banks (Fed, ECB, BoJ, BoE and similar) since the crisis, or the growth in their combined balance sheets, should be about $15–16 trillion; within about ±15% (roughly $13–18.5 trillion) counts as matching. True: both hold. Mostly true: the expansion age holds and the central-bank figure is in the right range but differs somewhat (e.g. $12–13 trillion or $18.5–20 trillion, or the figure fits total balance sheets rather than purchases). Mixed: one part holds and the other is clearly wrong. Mostly false: the expansion age is wrong by more than a year, or the asset figure is off by more than about 30%, while the other part is only loosely right. False: both are clearly wrong.

Set before the research began.

1. E1 Business Cycle Dating Committee Announcement September 20, 2010 National Bureau of Economic Research (NBER) · 20 September 2010

   “At its meeting, the committee determined that a trough in business activity occurred in the US economy in June 2009.”

2. E2 2nd Half 2018: Change in Size of Central Bank Balance Sheets Milliman FRM (via Advisor Perspectives) · 12 November 2018

   “As of the end of 2017, the Federal Reserve (Fed), European Central Bank (ECB) and Bank of Japan (BoJ) held combined assets worth approximately $14.4 trillion USD ($4.4T, $5.4T and $4.6T, respectively), representing nearly two-thirds of all the assets held by the world’s central banks.”

3. E3 2nd Half 2018: Change in Size of Central Bank Balance Sheets Milliman FRM (via Advisor Perspectives) · 12 November 2018

   “Year-to-date through October, the Fed has reduced the size of its balance sheet by approximately $310 billion or 6.9%, while the ECB and BoJ have expanded theirs by 3.4% and 5.8%, respectively.”

4. E4 January 2019 Newsletter: 4 Charts Every Investor Should Know Lyn Alden · 28 January 2019

   “This chart by DoubeLine shows the combined size of the major central bank balance sheets (about $15 trillion USD equivalent) and how as a whole they began shrinking in 2018, largely thanks to the Federal Reserve leading the way.”

E1 dates the US trough to June 2009, so the expansion was about 9.4 years old in November 2018, and the 'nine years' part holds. For the asset figure, E2 puts the Fed, ECB and BoJ balance sheets at about $14.4 trillion combined at end-2017. E3 shows only modest net changes through October 2018, and E4 describes major central bank balance sheets as about $15 trillion. These figures are total balance-sheet sizes, not cumulative purchases or growth since the crisis. The criteria treat a figure that fits total balance sheets rather than purchases as mostly true.