By PAUL WISEMANWASHINGTON (AP) â¿¿ Unemployment rates fell in 22 U.S. states in February from January, a sign that hiring gains are benefiting many parts of the country. The Labor Department said Friday that unemployment rates rose in 12 states and were unchanged in 16. Nationally, the unemployment rate slid to a four-year low of 7.7 percent in February, down from 7.9 percent in January. Since November, employers across the country have added an average of 200,000 jobs a month, nearly double the average from last spring. States hit hardest during the recession are showing improvement. In Nevada, unemployment dropped to 9.6 percent last month, down from 11.8 percent a year ago. That's the biggest year-over-year decrease among states. One reason for the big drop is that people have stopped applying for jobs. Nevada's work force â¿¿ those working or looking for work â¿¿ fell nearly 1 percent in the year through February. Only those looking for work are counted as unemployed. But hiring accelerated, too: Jobs in Nevada rose 2 percent over the past year. Unemployment in California fell to 9.6 percent last month, down from 10.8 percent in February 2012. California and Nevada are still tied with Mississippi for the nation's highest unemployment rate. Florida's job market has also rebounded in the past year. The Sunshine State's unemployment rate fell to 7.7 percent in February, down from 9 percent a year earlier. North Dakota once again held the nation's lowest unemployment rate, at 3.3 percent. The state is benefiting from a boom in oil and natural gas production. Nebraska had the second-lowest rate, at 3.8 percent. Overall, 42 states added jobs in February from January, and just eight lost jobs. The biggest monthly job gains came in Texas (up nearly 81,000) and California (up more than 41,000). In the 12 months up to February, Texas gained nearly 294,000 jobs, and California 128,000. On a percentage basis, North Dakota reported the fastest job growth over the past year, rising 5 percent.