The following ratings changes were generated on Tuesday, Jan. 6. We've upgraded Aecom Technology ( ACM), which provides professional technical and management support services to government and commercial clients worldwide, from sell to hold. Strengths its robust revenue growth, largely solid financial position with reasonable debt levels by most measures and impressive record of earnings per share growth. However, we also find weaknesses including weak operating cash flow and poor profit margins. Revenue rose by 46.2% since the same quarter a year ago, outpacing the industry average of 41.3% growth and helping to boost earnings per share. Aecom's debt-to-equity ratio of 0.3 is very low, though it is currently higher than that of the industry average, and the company maintains an adequate quick ratio of 1.3, which illustrates the ability to avoid short-term cash problems. Aecom's gross profit margin is extremely low at 6.7%, though it has managed to increased from the same period last year. The net profit margin of 2.7% trails the industry average. Net operating cash flow has decreased to $63.2 million, or 46% when compared with the same quarter last year. The stock is up 22% year over year and has clearly outperformed the S&P 500 over the same period. Although other factors naturally played a role, the company's strong earnings growth was key. Looking ahead, the stock's rise over the last year has already helped drive it to a level that is relatively expensive compared with the rest of its industry, implying reduced upside potential.