The stakes are high for San Diego’s housing market as the Federal Reserve tapers the national economy off super-low interest rates. Some experts think interest rates have been held back more by sluggish global growth than by Fed stimulus, so the “taper” that began this month won’t matter much. Then again, nobody can reliably forecast short-term rate movements. And there’s little question that higher rates would hurt potential home buyers. Already, skyrocketing mortgage payments may have chased away enough demand to halt price growth. Further increases would pile a new problem onto the region’s housing market, which is distorted by a chronic supply shortage and soaring costs caused by local and federal government polices. Waiting has certainly punished potential buyers lately. A typical new mortgage in San Diego County hit a modern low of $1,150 a month in February 2012.