It's kind of confusing because it depends on how you phrase it with percentages.
"The number of cores in the PC went up by 50%" means "there are now 1.5x as many cores"
However, "the number of cores in the PC is 50% what is was last year" means "there are now .5x as many cores"
In this case 200% is fairly unambiguous, but imagine a phrase like "scaling community 50% per year" which could mean different things depending on the direction of the scaling... I think it's more intuitive to use a multiplier: "scaling community 3x bigger per year" makes it easy to visualize an online community tripling in size every year.
"The number of cores in the PC went up by 50%" means "there are now 1.5x as many cores"
However, "the number of cores in the PC is 50% what is was last year" means "there are now .5x as many cores"
In this case 200% is fairly unambiguous, but imagine a phrase like "scaling community 50% per year" which could mean different things depending on the direction of the scaling... I think it's more intuitive to use a multiplier: "scaling community 3x bigger per year" makes it easy to visualize an online community tripling in size every year.