JPMorgan found that US households' equity allocations have risen to record highs.
It's not necessarily a bad sign for the stock market, as global holdings are still below peak levels.
Americans are holding a record-high amount of their investment portfolios in stocks, according to JPMorgan.
A group of strategists led by Nikolaos Panigirtzoglou find that the US households' equity allocation has risen to record highs, surpassing its previous high seen at the beginning of 2000, at the peak of the dotcom bubble.
The portfolio decision reflects a time when historically low interest rates have left investors with no choice but to put their money into stocks.
This record-high equity allocation may not be a negative sign for markets, the strategists added. That's because although US households are deeply invested in stocks, households around the globe including in Europe and Japan are still well below peak levels.
"We have to recognize that US household sector's equity allocation, by surpassing its previous historical high seen at the peak of the dotcom bubble, does present a vulnerability for the equity market going forward, JPMorgan said.
"At the same time, we also have to accept that the household sector outside the US is far from overextended and thus has room to propagate the equity market further from here. In other words, the risks from the household sector are not one-sided."
Examining the relative behavior of US versus non-US retail investors will be a key tool in assessing the strength of the global stock market from here, said JPMorgan.
In an earlier note in January, JPMorgan said that there's more room to run in the current bull market because global non-bank investors' equity holdings are still below the dangerous post- Global Financial Crisis levels.
At the moment, non-bank investors around the globe allocate 43.8% of their portfolios to equities, which is lower than the high of 47.6% seen in January 2018.