Buried in a NYT story about Passover, this statistic.

According to Lubicom, a marketing firm for the kosher food industry, about 350,000 households in the United States keep kosher kitchens year-round, a number that has gone up by 3 percent to 5 percent every year since 2005 as some American Jews have become more observant.

Seems high to me, but very interesting, especially that the number is said to be rising.