General Motors headquarters in Detroit. Photo Credit: General Motors Company.

It's been a solid year for Detroit's Big Three automakers in the U.S and each has gained market share at the expensive of their Japanese rivals Toyota (TM -3.23%) and Honda. Ford (F 0.69%) was the big winner halfway through the year; it increased U.S. market share from 15.7% to 16.5%. That doesn't seem like a big jump, but a fraction of a percentage is a big deal in the auto industry and Ford's gain was the most of any full-line automaker. When we look at global sales though, there's a different winner for the first half of 2013.

GM gains on Toyota
Toyota still ranks No. 1 in global sales for the first half of 2013, having sold 4.91 million units which is 1.2% fewer than last year. General Motors (GM 1.20%) came in just under its global rival at 4.85 million vehicles sold, and managed to top Toyota in quarterly sales for the first time in over a year. Part of the reason is that domestic automakers are surging in the U.S. market, whereas Toyota's sales declined 8.4% in its home market Japan – and that looks to continue.

"The decline in Japan will continue," said Jun Nokuo, an analyst with researcher R.L. Polk & Co. in Tokyo., according to Automotive News. "It is an aging society and the population is shrinking. At the same time, the popularity of cars is declining because public transportation is easy to use."

Another reason for Toyota's small slip in global sales was its territorial dispute in China that led to several quarters of drastic sales declines. Demand for Toyota's vehicles in China has been slow to recover, and last quarter its sales failed to climb even a full percentage point. GM, Volkswagen, and even Ford have all taken advantage of the Japanese decline in China and have witnessed their sales increase by double digits last quarter.

Some forget that this is a new development and GM held the global sales crown for seven decades before Toyota took the top spot in 2008. Since the recession, GM has been more focused on fixing the direction and financial stability of the company; it has watched almost helplessly as its vehicle portfolio became the oldest in the industry. This is the exact point in time where GM begins to change that with plans for the biggest refresh in company history – refreshing, redesigning, or replacing 90% of its vehicles by 2016 – which it hopes will help boost sales again.

Bottom line
Ford and GM battled through the recession, one taking a bailout to wipe debt from its books and one leveraging its blue oval namesake for a large loan to restructure on its own. Regardless of your feelings about how each company weathered the financial crisis, both have emerged much more stable and successful companies. Detroit is producing vehicles that people want to buy and that are available in smaller, popular, and more fuel-efficient segments.

I think that's why GM and Ford will continue to regain decades of lost market share in the U.S. and better expand globally. With GM's large head start over Ford internationally, it is the only domestic automaker with a chance to top Toyota anytime soon. I think it's very possible we'll witness GM break 10 million in global sales by 2015 – the first automaker to ever accomplish that feat. Now if GM can just take a page out of Ford's book and create a leaner operation, consolidate platforms, and improve economies of scale, then it could return to be the most dominant global automaker. Ultimately, both Ford and GM represent valuable investments as we watch the automotive industry rebound globally, even if Toyota holds the sales crown currently.