David Bianco, Deutsche Bank’s Chief U.S. Equity Strategist, was the subject of a Business Insider article on May 28, 2012, “David Bianco: The Stock Market Is Shrinking.” Bianco said that share buybacks by cash-rich companies was shrinking the available shares in the stock market, driving share prices up.
 
The term “Great Shrinkage” was popularized in the title of the Business Insider article on June 15, 2013, “The ‘Great Shrinkage’ Has Been A Much Bigger Stock Market Story Than The ‘Great Rotation’”. BI quoted Bianco:
 
“Buybacks have clearly been the dominant source of inflows into the equity market this year and last. We have always viewed the prospects of a great shrinkage more promising than a great rotation.”

The “Great Rotation” is when money flows out of bonds and into stocks. The financial term “Great Shrinkage” does not appear to hav been used at all prior to Bianco’s comments and the Business Insider articles.
   
   
Business Insider
David Bianco: The Stock Market Is Shrinking
Matthew Boesler May 28, 2012, 1:43 PM
Deutsche Bank’s controversial bull David Bianco has another reason to buy equities in his latest note to clients: share buybacks.
 
He writes that high cash balances of non-financial corporates, robust free cash flow measures and “abundant unused debt capacity” signal that “this vanishing of equities will accelerate despite higher dividend payout ratios,” driving a reduction in supply in the market for shares and thereby putting upward pressure on prices.
 
Business Insider
The ‘Great Shrinkage’ Has Been A Much Bigger Stock Market Story Than The ‘Great Rotation’
Sam Ro Jun. 15, 2013, 2:26 PM
Companies have been buying back stock like crazy lately.
 
Some are even taking advantage of cheap credit to finance buybacks with borrowed money.
 
Of course, many investors would rather see extra cash reinvested for growth.
 
But with limited opportunities in this slow growth environment and low returns on cash in this low interest rate environment, buybacks have been one of the favored methods for returning wealth to shareholders.
(...)
Here’s more color on buybacks from Bianco:
 
Shares shrink less than net dollars spent on buybacks of market cap because companies buy shares at higher prices than issued via employee stock option programs and rising stock prices put past option grants further into the money.
 
Buybacks have clearly been the dominant source of inflows into the equity market this year and last. We have always viewed the prospects of a great shrinkage more promising than a great rotation.