I would guess that's not _that_ low that it would have made an impact on those reading those reviews.
Chances are this has more to do with the limited, high-brow, circulation of these reviews. Harper's, for example, seems to have had a circulation of around 50,000 in 1851 (https://en.wikipedia.org/wiki/Harper%27s_Magazine#History). The USA had a population of about 23,000,000 at the time (https://en.wikipedia.org/wiki/1850_United_States_Census), so it would have reached less than 1% of the population.
I would guess that's not _that_ low that it would have made an impact on those reading those reviews.
Chances are this has more to do with the limited, high-brow, circulation of these reviews. Harper's, for example, seems to have had a circulation of around 50,000 in 1851 (https://en.wikipedia.org/wiki/Harper%27s_Magazine#History). The USA had a population of about 23,000,000 at the time (https://en.wikipedia.org/wiki/1850_United_States_Census), so it would have reached less than 1% of the population.