Total sales of video games, consoles and accessories fell 29 percent, to $849 million, in the U.S. last month, according to numbers released this afternoon by the NPD market research firm. It was the fifth straight monthly decline for the industry. So far this year, they've fallen 14 percent, to $8.16 billion. (Note: Monthly figures corrected since initial publication.)

The magnitude of the slowdown is evident in the accompanying chart, in which we've compiled NPD's monthly numbers for the three current-generation consoles -- Microsoft's Xbox 360, Sony's PlayStation 3 and Nintendo's Wii -- dating back to the beginning of last year. Pay no attention to the customary holiday peaks, but note the lower levels from January to June of this year, compared to the same period last year.

In the initial stages of the downturn, video games were seen as more resilient to the effects of the economy, but the latest numbers show that even they aren't immune.

NPD pointed out in today's report that the Xbox 360 is the only one of the three consoles to experience an increase in unit sales year-to-date, compared with the same seven months last year. Microsoft noted that Xbox 360 sales are up 17 percent over that period.

The Microsoft console came in at 202,900 units sold for July, compared with 121,800 for the PlayStation 3 and 252,500 for the Nintendo Wii.

Anita Frazier, an analyst with NPD, noted that the upcoming launches of games including Madden NFL, The Beatles: Rock Band, Halo 3: ODST and Call of Duty: Modern Warfare 2 should help matters in the coming months.

For July, Nintendo's Wii Sprts Resort with the Wii Motion Plus accessory led the rankings of video game software sales, at 508,200 units sold; followed by NCAA Football 2010 for Xbox 360, with 376,500 units sold on the Microsoft console.