(TNND) — Small business optimism continued its four-month slide in April, the National Federation of Independent Business showed Tuesday.

The NFIB Small Business Optimism Index ticked down 1.6 points in April to 95.8, with uncertainty dragging down the mood of America’s entrepreneurs.

The optimism index remained below the 51-year average of 98 for the second consecutive month.

Small business optimism reached a post-election high of 105.1 in December, buoyed by expectations of lower taxes and less regulation with President Donald Trump in the White House and Republicans in control of Congress.

But Trump’s tariffs have muddied the waters for a lot of small business owners.

The NFIB Uncertainty Index decreased a few points from March but remained far above the historical average.

NFIB Executive Director of Research Holly Wade said small business owners are reining in planned spending and investment.

"The level of uncertainty is really high, historically speaking, right now," Wade said. "And so, small business owners just don't have the level of confidence in economic conditions to move forward in investing in their business, whether that's capital spending or hiring plans."

Some small business owners are feeling the direct impact of shifting trade policies, she said.

Some have inventories sitting in a warehouse in China, with imports put on hold when 145% tariffs were imposed.

A lot of businesses also pulled forward their imports in anticipation of higher tariffs, Wade said.

U.S. and Chinese officials have agreed to back off the high tariffs for 90 days, cooling tensions in the brewing trade war.

The U.S., for its part, is temporarily dropping tariffs on China from 145% to 30%.

“That's still a very high tariff for many small business owners, but at least it allows some breathing room,” Wade said.

She said small business owners weren’t given a lot of time to react to Trump’s tariffs or plan for potential supply chain disruptions.

But the reprieve isn’t guaranteed to last beyond the 90 days, so small business owners are left wondering what environment they’ll be operating in by late summer.

Many owners, nearly 70%, see their business’ current health as "good" or "excellent."

Wade said that’s a great baseline from which they can operate, if not for the uncertainty.

The level of uncertainty has been elevated for a while now.

“The configuration of what they're uncertain about has changed a bit,” Wade said. “At the beginning, it was just the results of the election and how that might impact their business operations. And now it's turned into trade policy for some. It's immigration policy. So, the configuration is different, but the level of uncertainty is still historically very high.”

Labor quality was mentioned as the top problem by a fifth of small business owners.

Wade said it’s been especially hard for employers in the construction, transportation and manufacturing sectors to find enough good workers.

Inflation concerns are still prominent but have faded from their recent highs.

Fourteen percent of small business owners said inflation was their top problem, down from 22% a year ago.

Taxes ranked as another big concern, sandwiched between labor quality and inflation.

The NFIB’s optimism index is based on surveys from small companies across a broad scope of industries. The NFIB has collected small business economic trends data with quarterly surveys since 1973 and monthly surveys since 1986.