Upvoted for checking claims :-)

The link actually says that he cannot find the original source for the 9% number, but in the process found a 3% number.

I'll dig around for better numbers if I have time, but we can also look at significance from the other end:

State lotteries have become a significant source of revenue for the states, raising $17.6 billion in profits for state budgets in the 2009 fiscal year (FY) with 11 states collecting more revenue from their state lottery than from their state corporate income tax during FY2009.

(Wikipedia)

P.S. An interesting paper. Notable quotes:

The introduction of a state lottery is associated with a decline of $115 per quarter in household non-gambling consumption. This figure implies a monthly reduction of $23 in per-adult consumption, which compares to average monthly sales of $18 per lottery-state adult. The response is most pronounced for low-income households, which on average reduce non-gambling consumption by three percent. Among households in the lowest income third of the CEX sample, the data demonstrate a statistically significant reduction in expenditures on food eaten in the home (3.1 percent) and on home mortgage, rent, and other bills (6.9 percent).

And also

Based on 1998 sales data compiled by LeFleurs Inc., adults living in lottery states averaged $226 annually on lottery tickets. In contrast, CEX Diary respondents living in lottery states report an average of $0.71 for the two-week interval. Assuming smooth annual expenditures, this implies mean annual lottery expenditures of only $36. The underreporting is so severe that magnitudes implied by an analyses of this data are not reliable.