Nearly 500 million people are living in countries with negative interest rates, according to S&P Global, a factor which could fuel a return to a "cash-only" society.
Negative interest rates are designed to get money flowing in an economy. In theory, the rate, set by a central bank, discourages savers from holding on to their money because of the negative return and encourages banks to lend.
Central banks in Japan, euro zone and several other European countries have introduced negative interest rates, helping push the global stock of sub-zero-yielding sovereign debt to over $11 trillion.
But rather than spend more, negative rates may force consumers to look to hold their cash outside of the official banking sector.
"In Japan, we have got anecdotes that safes are actually being purchased for the storage of cash, much more so, because in Japan, there is a high propensity of the net households having a greater degree of savings and so instead of putting it in a bank deposit, they are keeping it under the mattress or basically in a safe," Andrew Paranthoiene, director at S&P Global Ratings, told CNBC in London on Friday.
Media reports suggest sales of mini-vaults to Japanese consumers have risen since the Bank of Japan introduced negative rates earlier this year.
Commerzbank and Munich Re in Germany have also considered stashing physical cash, according to media reports.
There are roughly 2 trillion euros ($2.3 trillion) in circulation and held by banks, which would fill 954,588 briefcases, 298 removal vans or 195 hotels rooms, the Financial Times reported this month.
Paranthoiene likened the situation to "going backwards in time."
"If negative interest rates spread beyond major financial institutions to the overall economy, the economy will shift increasingly towards a cash-only economy. This means increased transaction costs and rising risks of theft," S&P Global said in a large report forwarded to CNBC on Thursday.
"Some industries might benefit: Home protection services and safe manufacturers. You would be moving back toward a pure cash society. If nothing else, it's a cost in productivity. It gets more difficult and expensive to complete transactions. You really turn the clock back," it added.
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