Who is ADP's biggest competitor?

Inquiring minds want to know, who exactly stands as the primary rival to ADP in the realm of payroll and HR solutions? As the market landscape evolves, it's essential to stay abreast of the competitors vying for the top spot. Who is the formidable opponent that ADP consistently faces off against, vying for clientele and market share? Understanding this dynamic is key to navigating the industry's competitive waters.