THE bosses of foreign firms with operations in China grumble that their lives have got harder of late. China used to be a frontier market offering endless double-digit growth. Officials put out the welcome mat, and were open to wining and dining. Regulators were no more bothersome than in other emerging markets.Now, growth is slowing: official data released this week confirm that the economy grew by 7.4% last year, the slowest rate in 24 years.