The Fed only needs another 100 basis points of rate hikes as the economy is already showing signs of slowing, Wharton's Jeremy Siegel says

The Federal Reserve needs to raise its benchmark interest rate by 100 basis points in order to cool the US economy, according to a Wharton professor.

The Federal Reserve Chair was set to deliver a speech on monetary policy at the central bank's symposium in Jackson Hole, Wyoming. At 10 a.m., Powell was to speak. The time is eastern.

The market believes it will be a little more. Siegel thinks we won't need that much because of what he sees as a slowing economy.

In September, the Fed is expected to raise its rates. After starting the year with a low range of zero, the fed funds rate now stands at a range of 2% and 2.5%.

"I hope that Powell recognizes that the amount of tightening that we've put in and are expected to put in between now and year-end, at least 100 basis points, is very much slowing the economy," said Siegel.

Siegel said that the Fed should look at forward looking data such as "on the ground" real estate prices as they are starting to go down.

The data is backwards looking. Housing costs, which are a big factor of core inflation, are very lag in the way they are put into the index

The central bank's preferred inflation gauge, the PCE, came in at a 4.6% rate in July, up from 4.6% in June. Econoday's estimates for the reading were less than expected.

The headline inflation rate that includes energy and food was 8.5% in July, down from 9% in June.

The second-quarter gross domestic product was revised to show a contraction of 0.6%, less than the initial reading of 0.9%.