Can you clarify to what time period and data you are referring? I can really on speak with authority on the early colonial period, but Boyd-Bowman (1976) quantified Spanish immigration to the Americas from 1493-1600. In that time most of the migration to the Caribbean actually went to Hispaniola, which was the far more established colony, with 5-10 times more known arrivals. Those Hispaniola numbers though, were easily surpassed by immigration to Mexico and Peru, which typically saw about 3-4 times as many arrivals than that island.

So, at least through the 16th Century, Cuba was seeing very little immigration as compared to other regions in the Spanish Empire. I do know that Cuba saw measures taken to boost its population later on, but don't have the hard numbers. De la Fuente's Havana and the Atlantic in the Sixteenth Century notes several reductions in export/import duties to Havana which were specifically aimed at spurring growth, as well as an uptick in new immigrants coming from other parts of New Spain, as the easy money/opportunities dried up in places like Mexico and Peru.