In recent years, thanks to the advancements made in both technology and human understanding of pokémon as a whole, there aren’t many reports of this occurring. Usually, you may have at most thirty-five reports a year of a ghost-type consuming a human’s life force, and many of these occur simply because the victim insisted on trespassing into territory where they didn’t belong. (Three reports last year occurred in Burned Tower, for example.)
In years past, however, that number varied. From the turn of last century (when researchers began archiving and analyzing reports, rather than relying simply on folk knowledge of the type) to the 1960s, the number decreased steadily due to a combination of current events of the time and growing understanding of the type. Then, thanks to the popularity of the horror genre, the trends spiked to hundreds of reports per year as teens caught ghost-types but failed to handle them properly or ventured into ghost territory to perform “occult rituals” out of boredom. The number finally dropped in the 1980s and continued to decrease in subsequent years, as teens realized also thanks to the horror genre that perhaps disturbing ghost-types is a terrible past-time to have.
The Pokédex According to Bill 