The NFIB's Small Business Optimism Index, a seasonally adjusted measure of sentiment among small business owners, fell to 92.6 in March from 92.9 the previous month, the group announced Tuesday. That is the lowest reading since November 2013, and is 3.1 points below the figure for last March. (See also: 5 Biggest Challenges Facing Your Small Business.)

The largest declines from February were seen in the proportion of respondents who thought current inventory was "too low" (down 3 points to a net -5%) and those with job openings they could not fill (down 3 points to a net 25%), although there was a marked uptick in respondents who expect the economy to improve (up 4 points to a net -17%). The most commonly cited reason for saying it was "not a good time" to expand was economic conditions, followed by the political climate.

A net 22% reported lower earnings in the last three months compared to the previous three months. That is the lowest reading since October 2014. 

A net 9% said they expected to increase hiring in the next three months, a 1-point drop from February and a 3-point drop year-over-year.

Index component Seasonally adjusted level Change from February Change from March 2015
Plan to increase employment 9% -1 -3
Plan to make capital outlays 25% 2 3
Plan to increase inventories -2% -1 -3
Expect economy to improve -17% 4 -15
Expect real sales higher 1% 1 -13
Current inventory (net "too low" minus "too high") -5% -3 2
Current job openings 25% -3 1
Expected credit conditions -6% 1 0
Now a good time to expand 6% -2 -5
Earnings trends -22% -1 -1

The report's summary concludes that the small business sector "is underperforming, doing little more than operating in maintenance mode. Slow economic growth is now just a result of population growth, more haircuts, retail customers, health care patients, etc. But there is no exuberance, no optimism and not much hope, the numbers make it clear."