It is a classic "good news, bad news" problem for stock investors: Employment numbers are up (or down, it works either way).
Investors in the stock market are "owners" of the companies they invest in and as such are interested in anything that impacts earnings.
Labor costs are often a large part of a company's expenses. When unemployment is high, labor costs (wages) are held down because there is a large supply of workers looking for jobs.
Lower labor costs often translate into higher earnings for the company and smiles on stock owners faces. Especially after a protracted downturn in the economy, many companies have not only held wages down, but shed jobs as well.
This can make for very nice quarterly earnings reports.
However, there is another side to the employment numbers.
When unemployment is high, consumers may cut back on spending, either because a wage earner has lost a job or their hours have been reduced.
Other consumers may fear that their job could disappear also and begin saving more money (and spending less). This includes many stock owners.
And reduced consumer spending almost always puts a damper on economic growth. This means less demand for products and services and, eventually, less revenue and lower earnings for companies.
The sweet spot for employment numbers is for unemployment to be high enough to sustain an eager pool of applicants and low enough so consumer confidence is not shaken.