Insperity, Inc. NSP is benefiting from a booming professional employer organization (PEO) industry and rise in average number of worksite employees paid per month.In the past six months, shares of the company have gained 66%, massively outperforming the 1.6% growth of the industry it belongs to.With an expected long-term earnings per share growth rate of 18% and a market cap of $4.8 billion, Insperity seems to be a stock that investors should retain in their portfolio for now.Factors Driving Insperity’s PerformanceInsperity looks promising backed by a booming PEO industry. Notably, it offers a comprehensive suite of HR services’ solutions through PEO services known as Workforce Optimization and Workforce Synchronization solutions. With the help of these solutions, Insperity serves small and medium-sized businesses in selected markets across the United States. In second-quarter 2018, Insperity’s PEO solutions’ revenues from the United States grew 15.9% year over year. This marks an improvement from 14.9% revenue growth in first-quarter 2018. In 2017, the same increased 12.2% year over year.Apart from PEO services, Insperity is focusing on its Workforce Administration solution that provides human capital management and payroll services solution. By implementing Workforce Administration as the prime element of its next five-year plan, the company plans to offer the same as the most-integrated traditional employment solution in the market. In fact, Insperity remains highly optimistic about growth opportunities arising from Workforce Administration and Workforce Optimization.Insperity’s top-line growth is directly proportional to the rise in the average number of worksite employees paid per month. The company’s second-quarter 2018 revenues totaled $922.3 million (up 15.9% year over year), courtesy of a 13.1% increase in the average number of worksite employees paid per month and a 2.4% increase in revenues per worksite employee per month. Average number of worksite employees paid per month was 203.9 million and revenue per worksite employee per month came in at $1,507 in the same quarter.Worksite employee growth is benefiting from strength across new client sales, higher client retention and rise in net hiring of worksite employees by the company’s client base.Insperity, Inc. Price and Consensus Insperity, Inc. Price and Consensus | Insperity, Inc. QuoteTo ConcludeDespite riding on significant growth prospects, Insperity is not free from headwinds. The company continues to face high competition in the PEO industry and its earnings are seasonal in nature. However, we believe that worksite employee growth bodes well for Insperity and will continue to boost its top and bottom lines.Zacks Rank & Stocks to ConsiderCurrently, Insperity carries a Zacks Rank #3 (Hold). Some better-ranked stocks in the broader Business Services sector include Broadridge Financial Solutions BR, Paychex PAYX and Core-Mark Holding Company CORE. While Broadridge sports a Zacks Rank #1 (Strong Buy), Paychex and Core-Mark carry a Zacks Rank #2 (Buy). You can see the complete list of today’s Zacks #1 Rank stocks here.The long-term expected earnings per share growth rate for Broadridge Financial Solutions, Paychex and Core-Mark is 10%, 8.4% and 13%, respectively.Looking for Stocks with Skyrocketing Upside?Zacks has just released a Special Report on the booming investment opportunities of legal marijuana.Ignited by new referendums and legislation, this industry is expected to blast from an already robust $6.7 billion to $20.2 billion in 2021. Early investors stand to make a killing, but you have to be ready to act and know just where to look.See the pot trades we're targeting>>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Core-Mark Holding Company, Inc. (CORE): Free Stock Analysis Report Insperity, Inc. (NSP): Free Stock Analysis Report Paychex, Inc. (PAYX): Free Stock Analysis Report Broadridge Financial Solutions, Inc. (BR): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research