Yep, 75% coverage is too low for significant comprehension. You normally need 95% for decent comprehension and 98% for comfortable reading.
The coverage required in Japanese (my target language) seems something like the most frequent 15,000 words (depending on the definition of word) are required for 98% coverage. At 12,000 words it becomes viable to read with some comprehension and semi-frequent dictionary lookups.
Also, interestingly, you need about 2x the number of words in Japanese as English to reach 87% coverage:
"It has been reported that 2,000 high-frequent English words cover 87% of tokens (Nation, 1990). In case of Japanese, 4,024 SUWs are required to cover 87% of tokens." (Text Readability and Word Distribution in Japanese, Satoshi Sato)
The coverage required in Japanese (my target language) seems something like the most frequent 15,000 words (depending on the definition of word) are required for 98% coverage. At 12,000 words it becomes viable to read with some comprehension and semi-frequent dictionary lookups.
Also, interestingly, you need about 2x the number of words in Japanese as English to reach 87% coverage:
"It has been reported that 2,000 high-frequent English words cover 87% of tokens (Nation, 1990). In case of Japanese, 4,024 SUWs are required to cover 87% of tokens." (Text Readability and Word Distribution in Japanese, Satoshi Sato)