If instead you earned that income in Puerto Rico at a net effective tax rate of 15%âwhich can be easily achieved with Act 20 benefits for your business and a 4% tax on earningsâthen you would have $147,283 to invest to begin with. And plenty of available labor to expand rapidly. 2  The population of Puerto Rico is 3.7 million, a number that is slowly shrinking as more and more people emigrate to the US in search of workâsomething they can do freely as all Puerto Rican citizens are US citizens.