Here is a simple chart depicting the Federal Budget for 2011:
Source: Der Spiegel
Income Tax and social security contributions constitute over 50% and 37% of total revenue respectively. With high unemployment ans stagnant wages, this is bound to be under pressure for the foresseable future. With healthcare costs and other expenditures rising, the current deficit of $1.6 Trillion will also increase unless the economy improves and revenues increases.