He would have to use Quantitative Easing anyways
While my previous post talked about the variety of ways Paul Ryan should prefer an NGDP target over an inflation target, I realized that a lot of the Fed's policies that Paul opposes would still be necessary in a world of inflation targeting. In his 2010 Op-Ed with John Taylor, he called the quantitative easing programs "departures from rules-based monetary policy" that have "increased economic instability and endangered the central bank's independence." But would strict inflation targeting really solve the problem?
Below I've created a graph plotting quarterly annualized headline CPI inflation which includes commodity prices, the 2% inflation target, along with zones indicating when the two quantitative easing programs were hinted at and then executed. The dates for the QE announcements were taken from a conference paper, and they are used to show how policy and inflation were related.
As you can see, for much of the past four years, headline inflation was significantly below the 2% target traditionally set for the Fed. In response, the Fed hinted at the quantitative easing programs and drove up inflation. Yet Paul Ryan opposes these policy interventions. The question that I pose to Paul Ryan and his supporters is "what would you have had the Fed do during those time periods?" The short term interest rate was already at zero, so what would Ryan have suggested to fulfill the mandate? Paul would have been forced into unconventional monetary policy such as QE or Operation Twist just to fulfill his proposed mandate!
Under these conditions, there's no reason for Paul Ryan to not opt for an NGDP target instead. If you're going to be using unconventional monetary policy tools, you might as well use them to target a metric that is critical for stable, robust growth. An NGDP regime would be simple, rule based, and verifiable. So when choosing a monetary policy regime, why not NGDP level targeting?