The Dow Jones Industrial Average could soon do something it hasn’t done in more than 40 years, but it isn’t a milestone most investors will feel too happy about.

The blue-chip Dow DJIA, +0.02% has been struggling for nearly two weeks, pressured in large part by growing fears a series of spats between the U.S. and its trading partners could turn into a full-fledged trade war.

The index fell 0.8% on Thursday, a decline that marks the Dow’s eighth straight daily decline. This matches a stretch of losses that ended in March 2017. Should the index close lower on Friday, extending the streak to nine, that would mark the longest such stretch in just over 40 years.

According to the WSJ Market Data Group, the last time the Dow fell for nine straight trading days was a stretch that ended in February 1978, when the index traded at just under 750. It is at nearly 24,500 currently.

Going back to 1896, there have only been 10 instances when the average put together 9-day losing streaks. Should it do so again on Friday, it would mark the 11th. The Dow’s longest-ever losing streak was a 14-day stretch that ended in August 1941.

The last time the Dow closed in positive territory was on June 11, when it eked out a gain of 0.02%. Since then, it has dropped 3.3%, a milder decline than the nine-day drop seen in 1978, a period over which it fell 4.3%.

Losses in the Dow have been largely driven by rising trade tensions between the U.S. and China. Earlier this week, President Donald Trump threatened an additional $400 billion in tariffs against China. A spokesperson from China’s Ministry of Commerce said China would have no choice but to take comprehensive measures in response to the U.S.’s trade moves, the state-run Xinhua News Agency reported.

The issue has had an outsize impact on the Dow, as its 30 components are comprised primarily of huge multinational bellwethers. The degree to which a stock has overseas revenue exposure has been one of the primary factors dictating market moves of late; in contrast, the heavier U.S. focus of the Russell 2000 index RUT, -0.56% of small-capitalization shares has allowed that index to largely bypass trade uncertainty.

Read:Await a ‘technical pause’ before jumping on the small-cap stock rally, chart-watcher says

Also see:Small-cap stocks are on a tear — but shares in tiny companies have done better

According to FactSet, the Dow derives just 52.8% of its revenue from the U.S., meaning more is at risk from escalating trade tensions. In contrast, the Russell gets 78.6% of its revenue from the U.S., providing a bigger buffer against any escalation.

Read more: This one factor has determined which stocks rise or fall on trade-war fears