6.4 to 5.9 in 2000 but remains relatively high compared to the 1960s through the mid 1990s.
The number has risen due to the proliferation of new technology.
mnli hypothesis: The number has risen due to the proliferation of new technology. premise: 6.4 to 5.9 in 2000 but remains relatively high compared to the 1960s through the mid 1990s.