Business activity continued to grow at a solid clip for New York manufacturing firms surveyed in December, according to the Federal Reserve Bank of New York. The headline general business conditions index, at 18.0, remained close to last month's level. Thirty-seven percent of respondents reported that conditions had improved over the month, while 19 percent reported that conditions had worsened. The index for number of employees fell six points to 5.1, a level suggesting a small increase in employment levels. The average workweek index was zero, indicating that hours worked were unchanged.