If this value is negative, this is a bad sign that the company's liabilities exceed its ability to pay them. Company's that distribute a large amount of Stock dividends may also see this ratio value suffer, as it is burdened with constant dividend disbursements.
An increasing Net Worth Per Share value is a positive sign, as this may often be a signal the company has reduced its liabilities. The company may also have gone through a stock buy-back plan, reducing the number of shares, essentially making the net worth for each share more valuable.