The S&P/Case-Shiller home price index showed US home prices slumping for an eighth straight month in March, but prices in Houston are actually edging upward, based on median value of homes sold in Harris County in past months and years. While the multi-city composite of the S&P index has been steadily declining since August of last year, Houston's median home price reached its last low in November. The first-time homebuyer's tax credit is most likely the cause of a double dip in US home prices, as the market would otherwise have never had the boost to recover from the first dip. Houston's economy is considerably insulated from the US economy at large, and has many variables that keep it strong in the face of national trends. There is the port and all associated commerce, the petroleum industry, the energy corridor, the medical center, and many other corporate headquarters that keep the Houston economy from resembling that of the nation at large.